adds explanatory comment resets ubuntu version to latest

Author: chalmerlowe

.github/workflows/unittest.yml

@@ -22,6 +22,11 @@ jobs:
         python -m pip install --upgrade setuptools pip wheel
         python -m pip install nox
     - name: Run unit tests
+
+      # TODO 3.14 is not yet supported by pyarrow. See
+      # https://github.com/googleapis/google-cloud-python/issues/14686
+      # https://github.com/apache/arrow/issues/47438
+      # Reinstate running tests with 3.14 once this bug is fixed
       if: matrix.python != '3.14'
       env:
         COVERAGE_FILE: .coverage-${{ matrix.python }}