patch 8.2.0001: #endif comments do reflect corresponding #ifdef

Problem:    #endif comments do reflect corresponding #ifdef.
Solution:   Update the comments. (Rene Nyffenegger, closes #5351)
diff --git a/src/ui.c b/src/ui.c
index 7ec1e56..6359571 100644
--- a/src/ui.c
+++ b/src/ui.c
@@ -2356,9 +2356,9 @@
 	    ++inbufcount;
 	}
     }
-#endif // UNIX or VMS
+#endif // UNIX || VMS || MACOS_X
 }
-#endif // defined(UNIX) || defined(FEAT_GUI) || defined(VMS)
+#endif // USE_INPUT_BUF
 
 /*
  * Exit because of an input read error.