CAMEL-23703: camel-launcher - run package-native validation CI on JDK 21

Apache Camel's Maven build enforces JDK 21+ (enforce-java-version); both
validation jobs provisioned JDK 17. Bump to 21 so the enforcer passes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ammachado

.github/workflows/package-native-validation.yml

@@ -45,11 +45,11 @@ jobs:
         with:
           persist-credentials: false
 
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0
         with:
           distribution: 'temurin'
-          java-version: '17'
+          java-version: '21'
           cache: 'maven'
 
       - name: Prepare packages (stable, offline)
@@ -78,11 +78,11 @@ jobs:
         with:
           persist-credentials: false
 
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5.2.0
         with:
           distribution: 'temurin'
-          java-version: '17'
+          java-version: '21'
           cache: 'maven'
 
       - name: Prepare packages (stable, offline)