feat: Updated public cloud k8s tested versions

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Author: public-cloud-k8s-versions-check

.github/openshift_versions.json

@@ -1,9 +1,8 @@
 [
+  "4.20",
   "4.19",
   "4.18",
   "4.17",
   "4.16",
-  "4.15",
-  "4.14",
-  "4.12"
+  "4.14"
 ]