[GR-46719] Add jdk21 to common.jsonnet

PullRequest: graal/14871

Author: imanemamri

ci/common.jsonnet

@@ -63,6 +63,7 @@ local common_json = import "../common.json";
     "linux-jdk17": { packages+: { "devkit:gcc11.2.0-OL6.4+1": "==0" }},
     "linux-jdk19": { packages+: { "devkit:gcc11.2.0-OL6.4+1": "==0" }},
     "linux-jdk20": { packages+: { "devkit:gcc11.2.0-OL6.4+1": "==0" }},
+    "linux-jdk21": { packages+: { "devkit:gcc11.2.0-OL6.4+1": "==0" }},
   },
 
   # Dependencies