ci: restore full windows coverage

Since 01dce85, we don't have a CI job
on windows with coverage enabled which runs the full test suite. The
unittest/twisted ones only run `test_unittest.py`.

Enable coverage for one of the full jobs.

Author: bluetech

.github/workflows/test.yml

@@ -139,6 +139,7 @@ jobs:
             python: "3.14"
             os: windows-latest
             tox_env: "py314"
+            use_coverage: true
 
           # Use separate jobs for different unittest flavors (twisted, asynctest) to ensure proper coverage.
           - name: "ubuntu-py310-unittest-asynctest"