Fix TypedDataGenerator removal from DataProvider

Change-Id: Iadc8d58d790a6b42ab96bded68009191736705d7

server/src/com/vaadin/server/communication/data/typed/DataProvider.java

@@ -202,7 +202,7 @@ public abstract class DataProvider<T> extends AbstractExtension {
      *            typed data generator
      */
     public void removeDataGenerator(TypedDataGenerator<T> generator) {
-        generators.add(generator);
+        generators.remove(generator);
     }
 
     /**