[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