patch 9.1.0679: Rename from w_closing to w_locked is incomplete

Problem:  Rename from w_closing to w_locked is incomplete
          (after 9.1.0678).
Solution: Rename remaining occurrences of w_closing to w_locked and
          update comments (zeertzjq).

closes: #15504

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/structs.h b/src/structs.h
index abda3a0..847972f 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -3785,8 +3785,7 @@
     synblock_T	*w_s;		    // for :ownsyntax
 #endif
 
-    int		w_locked;	    // window is being closed, don't let
-				    // autocommands close it too.
+    int		w_locked;	    // don't let autocommands close the window
 
     frame_T	*w_frame;	    // frame containing this window