Update CI workflows to use JDK 21 with Oracle distribution

Changed Java version from 11 to 21 and switched distribution from 'adopt-hotspot' to 'oracle' in build and documentation publishing workflows for improved compatibility and support.

.github/workflows/build-on-pull-request.yml

@@ -22,11 +22,11 @@ jobs:
 
     steps:
       - uses: actions/checkout@v5
-      - name: Set up JDK 11
+      - name: Set up JDK 21
         uses: actions/setup-java@v5
         with:
-          java-version: '11'
-          distribution: 'adopt-hotspot'
+          java-version: '21'
+          distribution: 'oracle'
           server-id: github
           settings-path: ${{ github.workspace }}
 

.github/workflows/publish-docs.yml

@@ -30,11 +30,11 @@ jobs:
       url: ${{ steps.deployment.outputs.page_url }}
     steps:
       - uses: actions/checkout@v5
-      - name: Set up JDK 11
+      - name: Set up JDK 21
         uses: actions/setup-java@v5
         with:
-          java-version: '11'
-          distribution: 'adopt-hotspot'
+          java-version: '21'
+          distribution: 'oracle'
           server-id: github # Value of the distributionManagement/repository/id field of the pom.xml
           settings-path: ${{ github.workspace }} # location for the settings.xml file