4.1.1 mute button theming is broken

[awused]

Abstract

Steps to reproduce

1. Set theme to Photon
2. Update to 4.1.1

Expected result

Audio playing indicator/mute button looks like it did before.

Actual result

Mute button is giant and unthemed.

[awused]

The styling is also broken outright in the high contrast theme, with the foreground and background being the same colour.

[enzo-simone]

Same for me.

[Zelman88]

Also have this problem.

[enzo-simone]

Update: I do have this issue on a laptop running Linux Mint 22 Cinnamon, while it is not seen on another laptop running Ubuntu 20.04; both uses the latest available version of Firefox.