k8s 1.19&1.20 sys tests will be moved to CI pipeline only

Author: ChunyiLyu

.github/workflows/pr.yml

@@ -52,8 +52,6 @@ jobs:
     strategy:
       matrix:
         k8s:
-        - v1.19.11
-        - v1.20.7
         - v1.21.1
         rabbitmq-image:
         - rabbitmq:3.8.8-management