[FIX] web_editor: firefox `´ accent no break position

On firefox if we do for example:

ALT+GR + [ALT+GRable ´ key]

Firefox may send keys "AltGr" and "Dead" instead of just "AltGr".

This was possibly causing caret to go a position too low when writing
speedily with diacritical marks.

opw-1903865
closes #28739

addons/web_editor/static/lib/summernote/src/js/EventHandler.js

@@ -361,7 +361,7 @@ define([
             (keycode > 185 && keycode < 193) || // ;=,-./` (in order)
             (keycode > 218 && keycode < 223))) {   // [\]' (in order))
           eventName = 'visible';
-        } else if (!keycode) {
+        } else if (!keycode && event.key !== 'Dead') {
           self.invoke('restoreRange', $editable);
         }
         // ODOO: end_modification)