input: Make it possible to deactivate a modifier with any button for it

Before this change,
one could only deactivate a modifier with the same button that was
used to activate it.
Pressing another button for the same modifier did not work.

Part-of: <https://gitlab.gnome.org/World/Phosh/squeekboard/-/merge_requests/707>

src/layout.rs

@@ -1186,7 +1186,7 @@ mod seat {
                         key_id,
                         modifier, time,
                     ),
-                    false => submission.handle_drop_modifier(key_id, time),
+                    false => submission.handle_drop_modifier(key_id, modifier, time),
                 }
             }
             // only show when UI is present

src/submission.rs

@@ -228,10 +228,11 @@ impl Submission {
 
     pub fn handle_drop_modifier(
         &mut self,
-        key_id: KeyStateId,
+        _key_id: KeyStateId,
+        modifier: Modifier,
         _time: Timestamp,
     ) {
-        vec_remove(&mut self.modifiers_active, |(id, _)| *id == key_id);
+        vec_remove(&mut self.modifiers_active, |(_, m)| *m == modifier);
         self.update_modifiers();
     }