I dont think so, a colon is not a word to be corrected, and this is the only app or site I have encountered where it happens. Nowhere else does typing a colon initiate an emoji dropdown (its not changing the colon into an emoji, it is the equivalent of pressing an insert emoji button if such a thing existed)
It seems to put up the selection box for emoji choices that start with the colon character, like : ) (without the space) being a “slight smile” is in the list, and when you type the ) part it cuts the list down to just “slight smile”. If you don’t want emoji, just carry on typing without making a selection from that box, and it disappears once there are no possibles that start with what you have typed.
As an example, I can use the emoji selection to get a after just entering a : or I can carry on and type :) and NOT select the emoji and it appears as the old type smiley face. So it seems the easiest way to turn it off is to just ignore it when it pops up (or press space bar to force it to go away)!