Update Theora support for Chromium-based browsers and Firefox

[FormularSumo]

According to this Chrome platform status, Theora support was initially deprecated in Chrome 120 (already reflected in caniuse), and then planned to be disabled for all stable users by 16th January (which would have been Chrome 121 I think), and fully removed in Chrome 123. The Chromium bug tracker seems to say that it was actually 22nd January that it was disabled for all users, which should still have been 121, and then Chrome 124 when the remaining code and feature flags were removed.

Chrome 120 - 5/12/23
Chrome 121 - ?
Chrome 122 - 23/2/24

I find it quite hard to follow exactly when different releases rolled out (to how many people) and when this flag was disabed in stable (and for how many people), but seems to me that the most accurate thing would be to say it was disabled by default in 121 (rather than 120), and then fully removed in 124.

I've also tested on current stable versions of Chrome and Edge (126 for both) and confirmed that Theora playback does not work, and there's no flags to enable it anymore. The same files playback fine in stable Firefox (127) and other media players with Theora support.

On Firefox meanwhile, they deprecated and disabled by default in nightly in 126, with plans to remove and disable for beta and then stable users pretty soon. So I'd probably suggest putting a note on versions from 126 onwards saying similar to what Chrome says now, that it's being deprecated and to see that first bug for more details.