DO NOT MERGE. Matrix wrangling

Author: SamBarker

.github/workflows/ci.yml

@@ -92,6 +92,7 @@ jobs:
         include:
           - namespace: flink
             extraArgs: '--create-namespace --set "watchNamespaces={default,flink}"'
+            java-version: [ 21 ]
           - version: v1_20
             image: flink:1.20
           - version: v1_20
@@ -100,6 +101,7 @@ jobs:
             namespace: "default"
             test: test_application_operations.sh
             http-client: [ "okhttp", "vertx", "jetty",  "jdk"]
+            java-version: [ 21 ]
         exclude:
           - namespace: default
             test: test_multi_sessionjob.sh