deps: bump Masterminds/sprig to v3 (go.mod enabled version)

[radeksimko]

As can be seen from the go.mod diff, this bumps sprig to latest v3, which is go.mod-enabled.

This reduces the noise in go.mod which no longer has to track transitive dependencies.

Despite the major version bump, according to the changelog v2 -> v3 changes seem fairly minimal and don't affect Go API at all. It is worth calling out this update in cli's changelog though as behaviour changes may affect downstream consumers.

[egonbraun]

This also fixes the following security issue:

✗ Medium severity vulnerability found in github.com/Masterminds/goutils
  Description: Insecure Randomness
  Info: https://snyk.io/vuln/SNYK-GOLANG-GITHUBCOMMASTERMINDSGOUTILS-1296313
  Introduced through: github.com/mitchellh/cli@1.1.2
  From: github.com/mitchellh/cli@1.1.2 > github.com/Masterminds/sprig@2.22.0 > github.com/Masterminds/goutils@1.1.0
  Fixed in: 1.1.1

Is @mitchellh the only one that can approve your PR? I am getting the feeling I cannot rely on this project anymore since your PR was opened months ago. :/

Anyway, thanks for the PR and I hope it gets merged soon.