run sbt conflictingOverridesCheck as part of GH actions workflow

Author: memo33

.github/workflows/scala.yml

@@ -18,22 +18,28 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
-    - name: Set up JDK 17
+    - uses: actions/checkout@v4
+      with:
+        persist-credentials: false
+    - name: Set up JDK 21
       uses: actions/setup-java@v4
       with:
-        java-version: '17'
+        java-version: '21'
         distribution: 'temurin'
         cache: 'sbt'
     - uses: sbt/setup-sbt@v1
     - name: Run tests
       run: sbt test
     - name: Generate locale files
       run: sbt generateLocales
+    - name: Check for new conflicting RUL2 overrides
+      run: SBT_OPTS="-Xmx2G" sbt conflictingOverridesCheck
 
   lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
+      with:
+        persist-credentials: false
     - name: Check RUL2 syntax
       run: sh src/scripts/syntax-check-rul2.sh