refactor: remove test_notebook_snapshots.py

Removed redundant test_notebook_snapshots.py file as notebook examples
are already tested via the separate 'Test notebooks' CI step that
executes actual notebooks with jupyter nbconvert.

This simplifies the test suite and eliminates the slow snapshot tests
that were causing CI timeouts. The remaining test_notebooks.py file
provides sufficient snapshot coverage for key notebook examples.

Changes:
- Removed tests/test_notebook_snapshots.py (23 tests)
- Updated CI to exclude only test_notebooks.py
- Main test suite: 243 tests in ~9 seconds

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

Co-Authored-By: Claude <[email protected]>

Author: edeno

.github/workflows/release.yml

@@ -52,7 +52,7 @@ jobs:
       - name: Install dependencies
         run: pip install -e .[dev]
       - name: Run tests with coverage
-        run: pytest --cov=spectral_connectivity --cov-report=xml --cov-report=term-missing tests/ --ignore=tests/test_notebooks.py --ignore=tests/test_notebook_snapshots.py
+        run: pytest --cov=spectral_connectivity --cov-report=xml --cov-report=term-missing tests/ --ignore=tests/test_notebooks.py
       - name: Upload coverage to Codecov
         if: matrix.python-version == '3.12'
         uses: codecov/codecov-action@v5