doc: fix typo in submitting patches

Remove the article "an" before "incremental updates".

Signed-off-by: Swapnil Saste | INDIA <theswapnilsaste@gmail.Com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/SubmittingPatches

@@ -64,7 +64,7 @@ help you find out who they are.
   can still continue to further improve them by adding more patches on
   top, but by the time a topic gets merged to 'next', it is expected
   that everybody agrees that the scope and the basic direction of the
-  topic are appropriate, so such an incremental updates are limited to
+  topic are appropriate, so such incremental updates are limited to
   small corrections and polishing.  After a topic cooks for some time
   (like 7 calendar days) in 'next' without needing further tweaks on
   top, it gets merged to the 'master' branch and wait to become part