docs: fix code examples style in build doc

[alan-agius4]

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?

Code examples style is not consistent

What is the new behavior?

fix code examples styles

Does this PR introduce a breaking change?

• Yes
• No

Other information

[mary-poppins]

You can preview 7fa67e8 at https://pr26573-7fa67e8.ngbuilds.io/.

[jenniferfell]

Thanks for finding these and submitting fixes. A few small requests. Thanks!

[alan-agius4]

@jenniferfell, thanks for the review. Updated.

[brandonroberts]

@alan-agius4 will you rebase this branch so the tests will run again?

[alan-agius4]

@brandonroberts, done.

[mary-poppins]

You can preview 9c1c690 at https://pr26573-9c1c690.ngbuilds.io/.

[jenniferfell]

Thanks for making those changes. LGTM

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