Readme conflicts with setup.py about Python version support

[akx]

The README claims that releases after January 2024 will only support Python 3.8+, but the package is still marked to support Python 3.7+.

Can you clarify what the plans are for dropping Python 3.7 support for good?

Environment details

• OS: Irrelevant
• Python version: see below
• pip version: Irrelevant
• google-auth version: 2.27 (January 2024) forward

Steps to reproduce

1. Read the README about Python version support: https://github.com/googleapis/google-auth-library-python?tab=readme-ov-file#supported-python-versions
2. Read the setup.py about Python version support:

   google-auth-library-python/setup.py

   Line 64 in 40b9ed9

   python_requires=">=3.7",