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/ex_cmds.c b/src/ex_cmds.c
index 349269a..b2aaf1c 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -2838,7 +2838,7 @@
 		int	    did_decrement;
 		buf_T	    *was_curbuf = curbuf;
 
-		// Set the w_closing flag to avoid that autocommands close the
+		// Set the w_locked flag to avoid that autocommands close the
 		// window.  And set b_locked for the same reason.
 		the_curwin->w_locked = TRUE;
 		++buf->b_locked;