Option to disable emoji auto-completion

#### Is your feature request related to a problem? Please describe.

Typing the colon character (`:`) in the message input field opens an emoji auto-completer.
My keyboard already has an emoji picker and I find this auto-completion annoying/disturbing when composing messages.

#### Describe the solution you'd like.

It would be nice to introduce an option to let the user disable emoji auto-completion if they desire.

#### Describe alternatives you've considered.

I already tried the option added in #2664, but this only disables the button opening the emoji selector in the message input field, without disabling the auto-completer triggered when entering `:`.

#### Additional context

None.