Fix typo

Author: alvherre

src/backend/catalog/heap.c

@@ -1286,7 +1286,7 @@ heap_create_with_catalog(const char *relname,
 	/*
 	 * If this is an unlogged relation, it needs an init fork so that it can
 	 * be correctly reinitialized on restart.  Since we're going to do an
-	 * immediate sync, we ony need to xlog this if archiving or streaming is
+	 * immediate sync, we only need to xlog this if archiving or streaming is
 	 * enabled.  And the immediate sync is required, because otherwise there's
 	 * no guarantee that this will hit the disk before the next checkpoint
 	 * moves the redo pointer.