labeling PR should trigger builds again for all-contributors bot (#1682)

Author: ohbus

.github/workflows/maven-pr-builder.yml

@@ -29,7 +29,7 @@ name: Java PR Builder
 on:
  pull_request:
  branches: [ master ]
- types: [ opened, reopened, synchronize ]
+ types: [ opened, reopened, synchronize, labeled, unlabeled ]
 
 jobs:
  build: