Fix some typos

Author: Justin Pryzby
Discussion: https://postgr.es/m/20200408165653.GF2228@telsasoft.com

src/backend/access/transam/multixact.c

@@ -2666,7 +2666,7 @@ SetOffsetVacuumLimit(bool is_startup)
  * We use this to determine whether the addition is "wrapping around" the
  * boundary point, hence the name.  The reason we don't want to use the regular
  * 2^31-modulo arithmetic here is that we want to be able to use the whole of
- * the 2^32-1 space here, allowing for more multixacts that would fit
+ * the 2^32-1 space here, allowing for more multixacts than would fit
  * otherwise.
  */
 static bool

src/backend/partitioning/partbounds.c

@@ -1224,7 +1224,7 @@ merge_list_bounds(FmgrInfo *partsupfunc, Oid *partcollation,
 			Assert(inner_index >= 0);
 
 			/*
-			 * Try merging both paritions.  If successful, add the list value
+			 * Try merging both partitions.  If successful, add the list value
 			 * and index of the merged partition below.
 			 */
 			merged_index = merge_matching_partitions(&outer_map, &inner_map,