change a function name in a comment correctly

[Masahiro Ikeda]

Hi,

There is the comment which related function name is not same.
I attached the patch to fix it. Please review.

Regards,

--
Masahiro Ikeda
NTT DATA CORPORATION
diff --git a/src/backend/utils/cache/relfilenodemap.c b/src/backend/utils/cache/relfilenodemap.c
index 68b01ca68f..3acda32d17 100644
--- a/src/backend/utils/cache/relfilenodemap.c
+++ b/src/backend/utils/cache/relfilenodemap.c
@@ -82,7 +82,7 @@ RelfilenodeMapInvalidateCallback(Datum arg, Oid relid)
 }
 
 /*
- * RelfilenodeMapInvalidateCallback
+ * InitializeRelfilenodeMap
  *		Initialize cache, either on first use or after a reset.
  */
 static void