Update docker-build.yml to use Java 21

Author: nickpalladino

.github/workflows/docker-build.yml

@@ -23,11 +23,13 @@ jobs:
 
       - run: git pull origin ${{steps.extract_branch.outputs.branch}}
 
-      - name: Set up JDK 8
-        uses: actions/setup-java@v1.4.3
+      - name: Set up JDK 21
+        uses: actions/setup-java@v4
         with:
-          java-version: 8
-
+          distribution: temurin
+          java-version: '21'
+          cache: maven
+          
       - name: Build with Maven
         run: mvn clean install