Fix mismatched version comment for codecov-action (v5 -> v6.0.0)

Agent-Logs-Url: https://github.com/mongodb/mongo-python-driver/sessions/fb1d8b92-15c7-43db-ada3-75cdbe475b93

Co-authored-by: aclark4life <72164+aclark4life@users.noreply.github.com>

Author: Copilot

.github/workflows/test-python.yml

@@ -107,7 +107,7 @@ jobs:
       - name: Generate xml report
         run: uv tool run --with "coverage[toml]" coverage xml
       - name: Upload test results to Codecov
-        uses: codecov/codecov-action@57e3a136b779b570ffcdbf80b3bdc90e7fab3de2 # v5
+        uses: codecov/codecov-action@57e3a136b779b570ffcdbf80b3bdc90e7fab3de2 # v6.0.0
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
   doctest: