This PR fixes the glyph used for the option key in the new `Keybinding`
component.

Same fix as in #3065, but applied to the new `Keybinding` component so
that we don't regress when switching to GPUI2.

<img width="750" alt="Screenshot 2023-09-29 at 10 50 15 AM"
src="https://github.com/zed-industries/zed/assets/1486634/8c6147e9-fa05-4804-954c-b8e3b98cbdf0">

Release Notes:

- N/A