Add subtitles on/off option to KI settings in addition to audio settings

[dgelessus]

Trying to take home something useful from the very civil and reasoned (/s) discussion on the OU Discord yesterday...

The option for turning subtitles on/off is currently located in the audio settings. Some people have trouble finding it there and expected the option to be in the KI settings instead. I find that somewhat understandable, because the subtitles appear as KI text chat, and all other settings related to text chat (font size and fade time) are also in the KI settings.

I'd suggest adding a second on/off toggle for the subtitles into the KI settings, in the same style as the existing toggle for "Only accept private messages and KI mail from Buddies". The existing option in the audio settings should stay there, and the two options should be coupled, so that you can toggle subtitles in either of the two settings windows.

The only disadvantage I see here is that it could be confusing to have the same option in two places. We already have precedent for that though - the sound mute option is available both in the audio settings and as the "sound waves" button on the right side of the small KI. (Admittedly, the mute button on the KI is quite confusing if you don't know what it does - see #1220. But I think we won't have that problem with a clearly labeled toggle in the KI settings.)

[Hoikas]

FWIW, I don't think this is appropriate and am against including a duplicated option when the option is already in the objectively correct location.