Install Graphviz on the CI job

Author: ibbem

.github/workflows/maven.yml

@@ -15,6 +15,8 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+    - name: Install Graphviz
+      run: sudo apt-get install -y graphviz
     - uses: actions/checkout@v3
     - name: Set up JDK 17
       uses: actions/setup-java@v3