fix(bazel): Respect existing angular version

[kyliau]

If user has already installed Angular, Bazel should fetch the same
version. Otherwise, user will see an error in the post-install step
that performs version check.

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/master/CONTRIBUTING.md#commit
• 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?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.io application / infrastructure changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[mary-poppins]

You can preview 5042a28 at https://pr27495-5042a28.ngbuilds.io/.

[mary-poppins]

You can preview 0814a8e at https://pr27495-0814a8e.ngbuilds.io/.

[mary-poppins]

You can preview 6799ee2 at https://pr27495-6799ee2.ngbuilds.io/.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}