ci: upgrade GraalVM to Java 21 to match build toolchain

Author: Hayena

.github/workflows/assemble.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Setup Graal
         uses: graalvm/setup-graalvm@v1
         with:
-          java-version: '17'
+          java-version: '21'
           distribution: 'graalvm'
           github-token: ${{ secrets.GITHUB_TOKEN }}
 

.github/workflows/pull-request.yml

@@ -17,7 +17,7 @@ jobs:
       - name: Setup Graal
         uses: graalvm/setup-graalvm@v1
         with:
-          java-version: '17'
+          java-version: '21'
           distribution: 'graalvm'
           github-token: ${{ secrets.GITHUB_TOKEN }}