Fix md-lint and copilot instructions

[max-charlamb]

• Fixes md-lint issue from copilot in Update servicing branch naming convention for .NET 10+ #121328
• Updates copilot instructions to not have trailing whitespace in md files

[Copilot]

Pull Request Overview

This PR removes trailing whitespace from markdown files and adds a guideline to prevent future occurrences. The changes ensure consistency in markdown formatting across the repository.

• Removed trailing whitespace from three lines in the library servicing documentation
• Added a new guideline requiring no trailing whitespace in markdown files

Reviewed Changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/project/library-servicing.md	Removed trailing whitespace from lines 10, 39, and 58
.github/copilot-instructions.md	Added guideline requiring no trailing whitespace at the end of lines in markdown files

[max-charlamb]

/ba-g Docs only change