Sound split fixes in GUI and User Guide (#16609)
Various issues found in Sound Split feature description in the User Guide and in the GUI:
The User Guide does not explain the difference between "Sound split disabled" mode and "NVDA in both channels and applications in both channels" mode.
In the User Guide, the default option is called "Disabled sound split", but "Sound split disabled" in the GUI.
In the User Guide, the description of the way to restore the sound in both channels after a crash is not always correct, especially now that the "disabled" option does not modify audio processing at all.
The GUI warning when unchecking the Disabled mode is not correct since there are various other possible modes with speech in both channels (among them the new "NVDA both and app both"). The removal of this warning had been discussed and approved in Sound split #16071 (comment) but never completed.
Description of user facing changes
User Guide updated for 3 first items.
Warning removed from the GUI
