Build examples explicitly using JDK21

Author: adwsingh

examples/build.gradle.kts

@@ -10,4 +10,10 @@ subprojects {
             }
         }
     }
+
+    plugins.withId("java") {
+        the<JavaPluginExtension>().toolchain {
+            languageVersion.set(JavaLanguageVersion.of(21))
+        }
+    }
 }