Separate quality paragraphs and adjust decline wording

Split the quality-expectations section into two paragraphs (the warning
about low-quality contributions being declined was visually merged with
the preceding paragraph). Replace "and the pull request closed without
warning" with a note that maintainers may not always be able to provide
detailed feedback, which conveys the same practical reality.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: EliahKagan

CONTRIBUTING.md

@@ -15,8 +15,10 @@ Contributions must be made with care and meet the quality bar of the surrounding
 That means a change should not leave GitPython worse than it was before: it should be
 readable, maintainable, tested where practical, documented and consistent with the
 existing style and behavior.
+
 A contribution that works only narrowly but lowers the quality of the
-codebase may be declined, and the pull request closed without warning.
+codebase may be declined. The maintainers may not always be able to provide
+detailed feedback.
 
 ## AI-assisted contributions