Update gradle.yml

replaced master for main branch

Author: veltmanj

.github/workflows/gradle.yml

@@ -5,7 +5,7 @@ name: Java CI with Gradle
 
 on:
   push:
-    branches: [ master ]
+    branches: [ main ]
   schedule:
     # * is a special character in YAML so you have to quote this string
     - cron:  '0 6 * * *'