Fix a typo in add_partial_path

diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 0ac73984d2..34acb732ee 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -775,7 +775,7 @@ add_partial_path(RelOptInfo *parent_rel, Path *new_path)
 		/* Compare pathkeys. */
 		keyscmp = compare_pathkeys(new_path->pathkeys, old_path->pathkeys);
 
-		/* Unless pathkeys are incompable, keep just one of the two paths. */
+		/* Unless pathkeys are incompatible, keep just one of the two paths. */
 		if (keyscmp != PATHKEYS_DIFFERENT)
 		{
 			if (new_path->total_cost > old_path->total_cost * STD_FUZZ_FACTOR)