DO NOT MERGE. Further reduce the matrix for testing purposes

Author: SamBarker

.github/workflows/ci.yml

@@ -75,7 +75,7 @@ jobs:
     strategy:
       matrix:
         version: ["v1_20"]
-        namespace: ["default","flink"]
+        namespace: ["default"]
         mode: ["native" ]
         java-version: [ 21 ]
         http-client: [ "okhttp" ]
@@ -94,14 +94,6 @@ jobs:
             extraArgs: '--create-namespace --set "watchNamespaces={default,flink}"'
           - version: v1_20
             image: flink:1.20
-          - version: v1_19
-            image: flink:1.19
-          - version: v1_18
-            image: flink:1.18
-          - version: v1_17
-            image: flink:1.17
-          - version: v1_16
-            image: flink:1.16
           - version: v1_20
             # Version isn't critical but should ideally be latest.
             mode: "native"