terminal: remove OSC 9;4 terminal progress

[bluetech]

Due to compatibility issues with some terminal emulators. Can maybe try again in a few years.

Fix #13896.

[nicoddemus]

Oh this is a shame, it works well for ConEmu.

Could we try to keep the compatible ones working instead?

[The-Compiler]

nsI agree completely removing it would be a shame! I'm for either:

• Adding a configuration option to opt into it
• and/or enabling it on Windows by default (where the chance seems much higher that someone runs a compatible terminal and actually has the progress visible somewhere useful in the UI)

For the former, there is a risk we're polluting things with a new config option that won't be needed anymore hopefully a year down the line. At the same time, maybe there is still new/exotic/... terminal emulators that implement this the "broken" way (really a shame two extensions use the same number...), so it might still be needed in exotic cases.