Make apiClient beta

Author: MatKuhr

core/src/main/java/com/sap/ai/sdk/core/AiCoreService.java

@@ -138,6 +138,7 @@ public HttpDestination getDestinationForDeploymentByScenario(
    * @return A new client object based on {@link #getBaseDestination()}.
    */
   @Nonnull
+  @Beta
   public ApiClient getApiClient() {
     val destination = getBaseDestination();
     val httpRequestFactory = new HttpComponentsClientHttpRequestFactory();