Improve "Function Objects in the C++ Standard Library" article

[Rageking8]

• Bunch of cleanups and simple improvements
• Improve "Creating a Function Object" example:
  • operator() should return a bool since it's doing < comparisons
  • Use more descriptive names for clarity
• Update the syntax for set and remove_if
• Attempt to clarify that remove_if doesn't actually remove items from the container

[prmerger-automator]

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[learn-build-service-prod]

Learn Build status updates of commit d709f24:

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File	Status	Preview URL	Details
docs/standard-library/function-objects-in-the-stl.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.

[v-regandowner]

@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