Fix markdown query help formatting

[owen-mc]

Follow-up to #19730.

[Copilot]

Pull Request Overview

This PR standardizes and streamlines markdown query help formatting across multiple files. Key changes include renaming section headings (e.g. “Description” → “Overview”, “Recommendations” → “Recommendation”, “Examples” → “Example”) and updating reference list formatting to enforce a trailing full stop.

Reviewed Changes

Copilot reviewed 33 out of 33 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
ruby/ql/src/queries/variables/UninitializedLocal.md	Updated header titles and removed an extra context header.
java/ql/src/Violations of Best Practice/Undesirable Calls/DoNotCallFinalize.md	Reformatted headings and reference bullets.
java/ql/src/Performance/StringReplaceAllWithNonRegex.md	Changed heading to “## Overview” for clarity.
docs/query-help-style-guide.md	Enforced full-stop punctuation in reference items.
actions/ql/**	Applied consistent markdown heading changes and reference formatting updates across all action-related query files.