Drop explicit default Python version from CI

Author: puddly

.github/workflows/ci.yml

@@ -11,7 +11,6 @@ jobs:
     with:
       CODE_FOLDER: zigpy_zigate
       CACHE_VERSION: 2
-      PYTHON_VERSION_DEFAULT: 3.8.14
       PRE_COMMIT_CACHE_PATH:  ~/.cache/pre-commit
       MINIMUM_COVERAGE_PERCENTAGE: 46
     secrets: