fix(docs): master branch renaming

[hsynlms]

contributing.md file still refers master branch name since the branch renamed as main recently. This PR contains a fix for that.

related:
#33153
#33198

Bug

• Related issues linked using fixes #number
• Integration tests added
• Errors have helpful link attached, see contributing.md

Feature

• Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
• Related issues linked using fixes #number
• Integration tests added
• Documentation added
• Telemetry added. In case of a feature if it's used or not.
• Errors have helpful link attached, see contributing.md

Documentation / Examples

• Make sure the linting passes by running yarn lint

[timneutkens]

I've made a small edit to the description as it was no longer reflecting the reality. Should be good to land 👍

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
buildDuration	15.2s	15.4s	⚠️ +188ms
buildDurationCached	3.5s	3.4s	-33ms
nodeModulesSize	355 MB	355 MB	⚠️ +13 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.058	3.071	⚠️ +0.01
/ avg req/sec	817.54	813.98	⚠️ -3.56
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.405	1.379	-0.03
/error-in-render avg req/sec	1779.57	1812.64	+33.07

Client Bundles (main, webpack, commons)

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.2 kB	42.2 kB	✓
main-HASH.js gzip	27.2 kB	27.2 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	71 kB	71 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
_app-HASH.js gzip	1.37 kB	1.37 kB	✓
_error-HASH.js gzip	194 B	194 B	✓
amp-HASH.js gzip	312 B	312 B	✓
css-HASH.js gzip	326 B	326 B	✓
dynamic-HASH.js gzip	2.37 kB	2.37 kB	✓
head-HASH.js gzip	350 B	350 B	✓
hooks-HASH.js gzip	919 B	919 B	✓
image-HASH.js gzip	4.7 kB	4.7 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	2.13 kB	2.13 kB	✓
routerDirect..HASH.js gzip	321 B	321 B	✓
script-HASH.js gzip	383 B	383 B	✓
withRouter-HASH.js gzip	318 B	318 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	14.1 kB	14.1 kB	✓

Client Build Manifests

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
_buildManifest.js gzip	459 B	459 B	✓
Overall change	459 B	459 B	✓

Rendered Page Sizes

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
index.html gzip	531 B	531 B	✓
link.html gzip	545 B	545 B	✓
withRouter.html gzip	526 B	526 B	✓
Overall change	1.6 kB	1.6 kB	✓

---

Default Build with SWC (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
buildDuration	16.8s	16.9s	⚠️ +79ms
buildDurationCached	3.4s	3.4s	⚠️ +44ms
nodeModulesSize	355 MB	355 MB	⚠️ +13 B

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.042	3.075	⚠️ +0.03
/ avg req/sec	821.72	813.01	⚠️ -8.71
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.406	1.428	⚠️ +0.02
/error-in-render avg req/sec	1778.52	1750.91	⚠️ -27.61

Client Bundles (main, webpack, commons)

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
450.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	27.3 kB	27.3 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	71.3 kB	71.3 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	180 B	180 B	✓
amp-HASH.js gzip	305 B	305 B	✓
css-HASH.js gzip	321 B	321 B	✓
dynamic-HASH.js gzip	2.36 kB	2.36 kB	✓
head-HASH.js gzip	342 B	342 B	✓
hooks-HASH.js gzip	911 B	911 B	✓
image-HASH.js gzip	4.73 kB	4.73 kB	✓
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	2.19 kB	2.19 kB	✓
routerDirect..HASH.js gzip	314 B	314 B	✓
script-HASH.js gzip	375 B	375 B	✓
withRouter-HASH.js gzip	309 B	309 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	14.1 kB	14.1 kB	✓

Client Build Manifests

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
_buildManifest.js gzip	459 B	459 B	✓
Overall change	459 B	459 B	✓

Rendered Page Sizes

	vercel/next.js canary	hsynlms/next.js rename-master-branch	Change
index.html gzip	531 B	531 B	✓
link.html gzip	545 B	545 B	✓
withRouter.html gzip	526 B	526 B	✓
Overall change	1.6 kB	1.6 kB	✓

Commit: 9ea5ab3