Fix broken python github actions (streamlit#8580)

## Describe your changes
- Looks like pytest 8.2 breaks with tornado
- As a result, we should likely pin 8.1 pytest
- pytest-dev/pytest#12263
## GitHub Issue Link (if applicable)

## Testing Plan

- Explanation of why no additional tests are needed
- Unit Tests (JS and/or Python)
- E2E Tests
- Any manual testing needed?

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lib/test-requirements.txt

@@ -16,7 +16,9 @@ urllib3>=1.9
 # Testing infrastructure dependencies:
 hypothesis>=6.17.4
 parameterized
-pytest
+# Pinned for now because AsyncTest doesn't work with pytest 8.2.0
+# https://github.com/pytest-dev/pytest/issues/12263
+pytest<8.2.0
 pytest-cov
 requests-mock
 testfixtures