patch 8.2.1019: mapping <M-S-a> does not work in the GUI

Problem:    Mapping <M-S-a> does not work in the GUI.
Solution:   Move the logic to remove the shift modifier to
            may_remove_shift_modifier() and also use it in the GUI.

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1019,
 /**/
     1018,
 /**/