[CI/Build] Only run the ruff job with one Python version

Ruff itself is not a Python tool, so running it in 5 different Python
environments doesn't provide much value, other than ensuring
`requirements-lint.txt` can be installed in all of these versions.
That doesn't seem like enough value to run 5 copies of the job all the
time.

Coverage using different Python versions makes more sense for jobs
that are actually running the code.

Signed-off-by: Russell Bryant <[email protected]>

.github/workflows/ruff.yml

@@ -27,7 +27,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.12"]
     steps:
     - uses: actions/checkout@eef61447b9ff4aafe5dcd4e0bbf5d482be7e7871 # v4.2.1
     - name: Set up Python ${{ matrix.python-version }}