Fix Python 3.9 support and handle PR feedback

- Updated `pytest.ini` to ignore `FutureWarning` and `DeprecationWarning` regarding unsupported Python 3.9 version.
- Reverted the addition of `importlib-metadata` dependency in `setup.py` as requested by PR review (empty suggestion interpreted as removal).

Author: google-labs-jules[bot]

setup.py

@@ -43,7 +43,6 @@
     # Until this issue is closed
     # https://github.com/googleapis/google-cloud-python/issues/10566
     "google-cloud-core >= 1.4.4, < 3.0.0",
-    # "importlib-metadata >= 3.6.0; python_version < '3.10'", # Temp, confirm fix
 ]
 extras = {}