ci: set ci branch triggers

Author: matrei

.github/workflows/gradle.yml

@@ -2,10 +2,10 @@ name: "Java CI"
 on:
   push:
     branches:
-      - '[6-9]+.[0-9]+.x'
+      - '[6-9]+.x'
   pull_request:
     branches:
-      - '[6-9]+.[0-9]+.x'
+      - '[6-9]+.x'
   workflow_dispatch:
 jobs:
   test_project: