Small correction in Streaming Programming Guide doc

Corrected description of `repartition` function under 'Level of Parallelism in Data Receiving'.

Author: akkomar <[email protected]>

Closes #1079 from akkomar/streaming-guide-doc and squashes the following commits:

32dfc62 [akkomar] Corrected description of `repartition` function under 'Level of Parallelism in Data Receiving'.

(cherry picked from commit edb1f0e)
Signed-off-by: Reynold Xin <[email protected]>

Author: akkomar

docs/streaming-programming-guide.md

@@ -950,7 +950,7 @@ is 200 milliseconds.
 
 An alternative to receiving data with multiple input streams / receivers is to explicitly repartition
 the input data stream (using `inputStream.repartition(<number of partitions>)`).
-This distributes the received batches of data across all the machines in the cluster
+This distributes the received batches of data across specified number of machines in the cluster
 before further processing.
 
 ### Level of Parallelism in Data Processing