Fixes #issue. Correct SetNeedsLayout doc possessive

[Copilot]

Fixes

Proposed Changes/Todos

• Problem: Apply only review comment r3289975888 (suggested change) with no unrelated edits.
• Doc fix: In Terminal.Gui/ViewBase/View.Layout.cs, corrected the SetNeedsLayout XML comment from possessive typo to proper form.
• Code snippet:

  - /// ... indicating this View and all of it's subviews
  + /// ... indicating this View and all of its subviews

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
• My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• My code follows the Terminal.Gui library design guidelines
• I ran dotnet test before commit
• I have made corresponding changes to the API documentation (using /// style comments)
• My changes generate no new warnings
• I have checked my code and corrected any poor grammar or misspellings
• I conducted basic QA to assure all features are working