docs(test): fix doubled apostrophe in persist-hint test docstring

Address review: the docstring rendered the documented output form as
'<name>'' (two trailing apostrophes) instead of '<name>'. Docstring-only;
the assertions were already correct.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jawwad-ali

tests/extensions/git/test_git_extension.py

@@ -700,7 +700,7 @@ def test_output_omits_has_git_to_match_bash(self, tmp_path: Path):
 
     def test_persist_hint_matches_twins(self, tmp_path: Path):
         """The non-JSON SPECIFY_FEATURE hint must use the '# To persist in your
-        shell: $env:SPECIFY_FEATURE = '<name>'' form — matching the core
+        shell: $env:SPECIFY_FEATURE = '<name>' form — matching the core
         create-new-feature.ps1 twin and the bash/python twins of this script —
         not the old 'environment variable set to:' wording (the env var is only
         set in this child process, so the actionable output is the persist hint)."""