Update API models to not say 'image' in text gen fields.

[Efreak]

I hope this actually wprks properly, since I certainly can't test it on my tablet. If not, it should be an easy fix for someone who actually knows what they're doing...

Credit: Fripe pointed this out here, and I figured it'd be an easy fix. Then when I went to look, I remembered that the api reference is generated :(

[db0]

Hm, I dislike this duplication just for the text. Maybe we can word the next a bit more ambiguously so that it fits both?

[amiantos]

"generated this response" or "generated this content" instead of "image/text" could make sense