Updated JDK.

Author: svenrog

.github/workflows/build.yml

@@ -10,10 +10,10 @@ jobs:
     name: Build
     runs-on: windows-latest
     steps:
-      - name: Set up JDK 11
+      - name: Set up JDK 21
         uses: actions/setup-java@v1
         with:
-          java-version: 1.11
+          java-version: 21
       - uses: actions/checkout@v2
         with:
           fetch-depth: 0