keymap/ardumont: Fix substitute keycode reset step (#12675)

It so happens that when releasing the control key prior to the main key (C-h, C-i, C-n,
...), the substituted keycode was continuously sent in a loop after that (even when
releasing said key). The workaround so far was to type any other key to stop the loop.

This commit fixes such behavior by resetting the substitution keycode sent when the ctrl
released situation conditional is detected (and that the substitution keycode was on).

keyboards/keyboardio/atreus/keymaps/ardumont/keymap.c

@@ -97,8 +97,7 @@ bool substitute_keycode(uint16_t keycode, keyrecord_t *record, uint8_t mod_state
             // Do not let QMK process the keycode further
             return false;
         } else {
-            // In case substitude_keycode is still being sent even after the release of
-            // the key
+            // In case substitude_keycode is still even after release of the key
             if (key_registered) {
                 unregister_code(substitute_keycode);
                 key_registered = false;
@@ -106,6 +105,12 @@ bool substitute_keycode(uint16_t keycode, keyrecord_t *record, uint8_t mod_state
                 return false;
             }
         }
+    } else { // ctrl got released
+        // In case substitude_keycode is still sent after release of the ctrl key
+        if (key_registered) {
+            unregister_code(substitute_keycode);
+            key_registered = false;
+        }
     }
     // Else, let QMK process the keycode as usual
     return true;