Add option to turn off "hit ALT for prediction" popup

[danfuzz]

When in "subtle" edit prediction mode, Zed seems to like to overlay a little hint that reminds one that they can press ALT to get a prediction:

I see the utility in adding a prediction preview when there are other possible completions (that is, from the language server), but, speaking personally, this little giblet by itself is annoying and distracting, and I'd love to have a setting to turn it off without turning off edit predictions entirely.

[remorses]

An alternative would be to use a different color the cursor, for example make it red when there is a prediction available

[claudio4]

I would really love this.

I want to test and to have readily available the AI suggestions when I invoke them, but if I am not interacting with them, I do not wish for distractive elements to try to grab my attention while I work.

[matt-h]

Agree, I use the AI completions rarely, it seems like a waste to always be looking for predictions and popping up with the annoying popup here.

Ideally, I want it off but will then look for predictions when I press the key.