fix github actions

Author: sunny-chung

.github/workflows/deploy-website.yaml

@@ -25,6 +25,10 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v3
+      - uses: actions/setup-java@v3
+        with:
+          distribution: 'corretto'
+          java-version: '21'
       - run: ./gradlew :kotlite-apidoc:generateStdlibApiDoc :kotlite-demo:assemble
       - run: cd doc && asciidoctor -r asciidoctor-diagram -D "/wd/doc/output" /wd/doc/usermanual/index.adoc
       - run: cp -R usermanual/img output/img

.github/workflows/run-test.yaml

@@ -19,5 +19,5 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'corretto'
-          java-version: '17'
+          java-version: '21'
       - run: ./gradlew check -PCICD=GitHubActions # the "clean" task would fail on GitHub Actions: https://github.com/sunny-chung/kdatetime-multiplatform/actions/runs/8213856523/job/22465724399