text: Title: setuptools' tests_require deprecation
  Body: **Describe the bug**
  when running `pip install -v .` in the pytest-flask project directory, setuptools produces a warning:
  
  ```
  /tmp/pip-build-env-gy9vaagi/overlay/lib/python3.12/site-packages/setuptools/_distutils/dist.py:261: UserWarning: Unknown distribution option: 'tests_require'
    warnings.warn(msg)
  ```
  
  it seems that tests_require was removed - it was deprecated for a while: https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-tests-require
  
  test_require seems to be empty anyway, probably best to just drop it
  
  **To Reproduce**
  Steps to reproduce the behavior:
  1. pip install -v .
  
  **Expected behavior**
  no warning
  
  **Screenshots**
  If applicable, add screenshots to help explain your problem.
  
  **Environment (please complete the following information):**
   - OS: [e.g. macOS Catalina]: Gentoo GNU/Linux
   - Python Version [e.g. 3.8.5]: 3.12.8
   - pytest-flask version [e.g. 0.15.0]: trunk