ci: Drop Python 3.9 checks (#2093)

Removed 'Unit Tests (Python 3.9)' from required status checks.

Author: tisonkun

.asf.yaml

@@ -43,7 +43,6 @@ github:
     trunk:
       required_status_checks:
         contexts:
-          - "Unit Tests (Python 3.9)"
           - "Unit Tests (Python 3.10)"
           - "Unit Tests (Python 3.11)"
           - "Unit Tests (Python 3.12)"