Update docs/tutorials/cooperative_groups_tutorial.rst

Co-authored-by: Leo Paoletti <[email protected]>

docs/tutorials/cooperative_groups_tutorial.rst

@@ -159,7 +159,7 @@ results are stored in global memory.
 3. The reduction of custom partition
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-In this code section the sum is calculate on thread_block_group level, then the
+In this code section, the sum is calculated on the thread_block_group level, then the
 results are stored in global memory.
 
 .. code-block:: cpp