Upgrade JDK to 21 and clean up Maven workflow

Updated the JDK version from 17 to 21 in the Maven CI workflow. Removed unnecessary comments and the dependency graph update step.

Author: otaviojava

.github/workflows/maven.yml

@@ -0,0 +1,23 @@
+name: Java CI with Maven
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up JDK 21
+      uses: actions/setup-java@v4
+      with:
+        java-version: '21'
+        distribution: 'temurin'
+        cache: maven
+    - name: Build with Maven
+      run: mvn -B package --file pom.xml