fix: upgrade Java to 21 for Capacitor Android plugin

Author: Johann

.github/workflows/build-android.yml

@@ -25,7 +25,7 @@ jobs:
         uses: actions/setup-java@v4
         with:
           distribution: "temurin"
-          java-version: "17"
+          java-version: "21"
 
       - name: Install dependencies
         run: npm ci