Update validate.yml

Author: MaikuB

.github/workflows/validate.yml

@@ -56,7 +56,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: 'zulu'
-          java-version: '17'
+          java-version: '21'
       - uses: subosito/flutter-action@v2
         with:
           channel: stable
@@ -74,7 +74,7 @@ jobs:
         - uses: actions/setup-java@v4
           with:
             distribution: 'zulu'
-            java-version: '17'
+            java-version: '21'
         - uses: subosito/flutter-action@v2
           with:
             channel: stable
@@ -253,7 +253,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: 'zulu'
-          java-version: '17'
+          java-version: '21'
       - uses: subosito/flutter-action@v2
         with:
           channel: stable
@@ -291,7 +291,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: 'zulu'
-          java-version: '17'
+          java-version: '21'
       - uses: subosito/flutter-action@v2
         with:
           channel: stable