fix: update pnpm install flags

[jmcdo29]

pnpm v7.0.0 until 7.13.5 uses --strict-peer-dependencies=true which causes a failure when not all peerDependencies are installed. By setting the flag explicitly, this will no longer be a problem for new users.

fix: #1806

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[X] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

When a user uses pnpm 7.0.0 to 7.13.5 the install portion of nest new fails because of the strict-peer-dependencies option being set inherently to true, as we do not add every peer dependency to the package.json

Issue Number: #1806

What is the new behavior?

nest new will no longer fail for pnpm v7.0.0 to 7.13.5. Later versions it should be set to false by default anyways

Does this PR introduce a breaking change?

[ ] Yes
[X] No

Other information

[kamilmysliwiec]

lgtm