chore(gapic): remove Python 3.9 templates and update workflow matrix

Author: chalmerlowe

.github/workflows/gapic-generator-tests.yml

@@ -18,7 +18,7 @@ env:
   SHOWCASE_VERSION: 0.35.0
   PROTOC_VERSION: 3.20.2
   LATEST_STABLE_PYTHON: 3.14
-  ALL_PYTHON: "['3.9', '3.10', '3.11', '3.12', '3.13', '3.14']"
+  ALL_PYTHON: "['3.10', '3.11', '3.12', '3.13', '3.14']"
 
 jobs:
   check_changes: