Correct some accidental renames

IDE over-eagerly replaced some occurrences of createAggregator with
createAggregatorForDoFn. This corrects that.

sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/Aggregator.java

@@ -25,7 +25,7 @@
  * to be combined across all bundles.
  *
  * <p>Aggregators are created by calling
- * {@link OldDoFn#createAggregator OldDoFn.createAggregatorForDoFn},
+ * {@link OldDoFn#createAggregator OldDoFn.createAggregator},
  * typically from the {@link OldDoFn} constructor. Elements can be added to the
  * {@code Aggregator} by calling {@link Aggregator#addValue}.
  *
@@ -41,7 +41,7 @@
  *   private Aggregator<Integer, Integer> myAggregator;
  *
  *   public MyDoFn() {
- *     myAggregator = createAggregatorForDoFn("myAggregator", new Sum.SumIntegerFn());
+ *     myAggregator = createAggregator("myAggregator", new Sum.SumIntegerFn());
  *   }
  *
  *   @Override
@@ -83,15 +83,15 @@ interface AggregatorFactory {
      *  class of the {@link OldDoFn} being executed and the context of the step it is being
      *  executed in.
      */
-    <InputT, AccumT, OutputT> Aggregator<InputT, OutputT> createAggregatorForDoFn(
+    <InputT, AccumT, OutputT> Aggregator<InputT, OutputT> createAggregator(
         Class<?> fnClass, ExecutionContext.StepContext stepContext,
         String aggregatorName, CombineFn<InputT, AccumT, OutputT> combine);
   }
 
   // TODO: Consider the following additional API conveniences:
-  // - In addition to createAggregatorForDoFn(), consider adding getAggregator() to
+  // - In addition to createAggregator(), consider adding getAggregator() to
   //   avoid the need to store the aggregator locally in a OldDoFn, i.e., create
   //   if not already present.
   // - Add a shortcut for the most common aggregator:
-  //   c.createAggregatorForDoFn("name", new Sum.SumIntegerFn()).
+  //   c.createAggregator("name", new Sum.SumIntegerFn()).
 }

sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/DoFnTester.java

@@ -667,7 +667,7 @@ protected <AggInputT, AggOutputT> Aggregator<AggInputT, AggOutputT> createAggreg
         String name, CombineFn<AggInputT, ?, AggOutputT> combiner) {
       throw new IllegalStateException("Aggregators should not be created within ProcessContext. "
           + "Instead, create an aggregator at OldDoFn construction time with"
-          + " createAggregatorForDoFn, and ensure they are set up by the time startBundle is"
+          + " createAggregator, and ensure they are set up by the time startBundle is"
           + " called with setupDelegateAggregators.");
     }
   }