[hotfix] Fix typo in WindowedStream.

This closes apache#6825.

flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/WindowedStream.java

@@ -1011,7 +1011,7 @@ public <ACC, V, R> SingleOutputStreamOperator<R> aggregate(
 	 * evaluation of the window for each key individually. The output of the window function is
 	 * interpreted as a regular non-windowed stream.
 	 *
-	 * <p>Not that this function requires that all data in the windows is buffered until the window
+	 * <p>Note that this function requires that all data in the windows is buffered until the window
 	 * is evaluated, as the function provides no means of incremental aggregation.
 	 *
 	 * @param function The window function.
@@ -1045,7 +1045,7 @@ public <R> SingleOutputStreamOperator<R> apply(WindowFunction<T, R, K, W> functi
 	 * evaluation of the window for each key individually. The output of the window function is
 	 * interpreted as a regular non-windowed stream.
 	 *
-	 * <p>Not that this function requires that all data in the windows is buffered until the window
+	 * <p>Note that this function requires that all data in the windows is buffered until the window
 	 * is evaluated, as the function provides no means of incremental aggregation.
 	 *
 	 * @param function The window function.
@@ -1063,7 +1063,7 @@ public <R> SingleOutputStreamOperator<R> process(ProcessWindowFunction<T, R, K,
 	 * evaluation of the window for each key individually. The output of the window function is
 	 * interpreted as a regular non-windowed stream.
 	 *
-	 * <p>Not that this function requires that all data in the windows is buffered until the window
+	 * <p>Note that this function requires that all data in the windows is buffered until the window
 	 * is evaluated, as the function provides no means of incremental aggregation.
 	 *
 	 * @param function The window function.