Fix malformed anchor in headers

[Rageking8]

Fix problem where a malformed anchor causes a whole chunk of text to be rendered as a link.

See MicrosoftDocs/visualstudio-docs#10362 for an example of the malformed rendering.

The bulk of the regression was introduced in 45d31cd.

[prmerger-automator]

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

[learn-build-service-prod]

Learn Build status updates of commit ec32162:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/build/arm64ec-windows-abi-conventions.md	✅Succeeded
docs/build/reference/contents-of-a-makefile.md	✅Succeeded
docs/build/reference/creating-a-makefile-project.md	✅Succeeded
docs/build/reference/defining-an-nmake-macro.md	✅Succeeded
docs/build/reference/inference-rules.md	✅Succeeded
docs/build/reference/inline-files-in-a-makefile.md	✅Succeeded
docs/build/reference/makefile-preprocessing.md	✅Succeeded
docs/build/reference/special-nmake-macros.md	✅Succeeded
docs/build/reference/using-an-nmake-macro.md	✅Succeeded
docs/cpp/if-else-statement-cpp.md	✅Succeeded
docs/cpp/main-function-command-line-args.md	✅Succeeded
docs/cppcx/platform-intptr-value-class.md	✅Succeeded
docs/mfc/reference/cmfcbutton-class.md	✅Succeeded
docs/mfc/reference/extension-dll-macros.md	✅Succeeded
docs/parallel/amp/reference/concurrency-direct3d-namespace-functions-amp.md	✅Succeeded
docs/parallel/amp/reference/concurrency-precise-math-namespace-functions.md	✅Succeeded
docs/parallel/amp/reference/norm-3-class.md	✅Succeeded
docs/parallel/amp/reference/tile-barrier-class.md	✅Succeeded
docs/parallel/concrt/reference/reader-writer-lock-class.md	✅Succeeded
docs/standard-library/scoped-allocator-adaptor-class.md	✅Succeeded

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PRMerger Results

Issue	Description
Changed Files	This PR contains more than 10 changed files.

[Court72]

@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]

@Rageking8, the format that's in there seems to work fine. I have no objection to the long form so will merge this.

[TylerMSFT]

#sign-off