[dsm] comment typo

In the following sentence, I believe either 'the' or 'a' should be kept, not
both. I here keep the 'the', but feel free to change.

---
 src/backend/storage/ipc/dsm_impl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/backend/storage/ipc/dsm_impl.c
b/src/backend/storage/ipc/dsm_impl.c
index 6399fa2ad5..19a9cfc8ac 100644
--- a/src/backend/storage/ipc/dsm_impl.c
+++ b/src/backend/storage/ipc/dsm_impl.c
@@ -137,7 +137,7 @@ int min_dynamic_shared_memory;
  * Arguments:
  * op: The operation to be performed.
  * handle: The handle of an existing object, or for DSM_OP_CREATE, the
- *    a new handle the caller wants created.
+ *    new handle the caller wants created.
  * request_size: For DSM_OP_CREATE, the requested size.  Otherwise, 0.
  * impl_private: Private, implementation-specific data.  Will be a pointer
  *    to NULL for the first operation on a shared memory segment within this
-- 

-- 
Regards
Junwang Zhao