Update GraphServiceClient.java

missing import

Author: raghucha

src/main/java/com/microsoft/graph/serviceclient/GraphServiceClient.java

@@ -2,6 +2,7 @@
 
 import com.microsoft.graph.core.CoreConstants;
 import com.microsoft.graph.core.requests.BaseGraphRequestAdapter;
+import com.microsoft.graph.core.requests.BaseGraphRequestAdapter.Clouds;
 import com.microsoft.graph.core.requests.BatchRequestBuilder;
 import com.microsoft.graph.core.requests.options.GraphClientOption;
 import com.microsoft.graph.core.requests.IBaseClient;