Disable Sonar check on forks

Author: andreaTP

.github/workflows/sonar.yml

@@ -15,6 +15,7 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
+    if: github.repository == 'java-operator-sdk/java-operator-sdk'
     steps:
       - uses: actions/checkout@v2
       - name: Set up Java and Maven