Use latest docker image for plugin ITs (#1127)

Author: nils-werner-sonarsource

.cirrus.yml

@@ -101,7 +101,6 @@ plugin_qa_task:
     - build
   only_if: $CIRRUS_PR != "" || $CIRRUS_BRANCH == "master" || $CIRRUS_BRANCH =~ "branch-.*"
   gke_container:
-    image: gcr.io/language-team/base:v1
     <<: *CONTAINER_DEFINITION
     cpu: 3
     memory: 8G