Update PyPy versions in GitHub Actions workflow

- Remove deprecated pypy-3.6, pypy-3.7, pypy-3.8 (no longer supported)
- Add pypy-3.11 (current main PyPy version)
- Keep pypy-2.7, pypy-3.9, pypy-3.10 for compatibility

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: evhub

.github/workflows/run-tests.yml

@@ -17,11 +17,9 @@ jobs:
           - '3.13'
           - '3.14'
           - 'pypy-2.7'
-          - 'pypy-3.6'
-          - 'pypy-3.7'
-          - 'pypy-3.8'
           - 'pypy-3.9'
           - 'pypy-3.10'
+          - 'pypy-3.11'
       fail-fast: false
     name: Python ${{ matrix.python-version }}
     steps: