googleapis-common-protos defining deprecated license classifier

The wheel metadata of the package do contain a license classifier which is deprecated (see [PEP 639](https://peps.python.org/pep-0639/#deprecate-license-classifiers)). Since the `project.license.text` is already SPDX-compliant, the redundant classifier can be safely removed from `project.classifiers` in `pyproject.toml`. 

Reproduced via:

```bash
❯ cd packages/googleapis-common-protos
❯ uv build .
❯ unzip -qo dist/googleapis_common_protos-1.75.2-py3-none-any.whl
❯ grep License googleapis_common_protos-1.75.2.dist-info/METADATA
License: Apache 2.0
Classifier: License :: OSI Approved :: Apache Software License # <-- this is deprecated
License-File: LICENSE
```

When building the package via `uv build .` one can also observe the deprecation warning in the logs:

```log     
********************************************************************************
Please consider removing the following classifiers in favor of a SPDX license expression:

License :: OSI Approved :: Apache Software License

See https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license for details.

********************************************************************************
```

I'm happy to open a PR after approval.

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