Updates for vector class template reference

[Rageking8]

Summary:

• Fix missing period and semicolon
• Fix broken link to #allocator_type
• Fix broken comment on vector_assign.cpp
• Improve examples
  • Normalize all formatting (4 space indents, no excessive space around parentheses and angle brackets, template and brace on a new line, and others)
  • Remove dead code and superfluous includes
  • Add missing Output code block where appropriate
  • Test all examples to check that they compile and that the Output part is correct

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[learn-build-service-prod]

Learn Build status updates of commit 70ce14a:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/standard-library/vector-class.md	✅Succeeded

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[prmerger-automator]

PRMerger Results

Issue	Description
File Change Percent	This PR contains file(s) with more than 30% file change.

[prmerger-automator]

@Rageking8 : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[ttorble]

@TylerMSFT

Can you review the proposed changes?

IMPORTANT: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team

[TylerMSFT]

This is better. Thanks for fixing typos and I particularly appreciate you adding the output sections! Your work is very much appreciated!

[TylerMSFT]

#sign-off