Fix test suite freeze
Fix test suite freeze

The issue is that the `test/regression/2056-assert-on-small-window`
sent JSON UI input without waiting for for the JSON UI to be
initialized.

Closes #3196

Somasis/kakoune,lenormf/kakoune,lenormf/kakoune,danr/kakoune,casimir/kakoune,alexherbo2/kakoune,jkonecny12/kakoune,danr/kakoune,Somasis/kakoune,occivink/kakoune,occivink/kakoune,occivink/kakoune,lenormf/kakoune,lenormf/kakoune,alexherbo2/kakoune,mawww/kakoune,danr/kakoune,Somasis/kakoune,mawww/kakoune,alexherbo2/kakoune,jkonecny12/kakoune,casimir/kakoune,jkonecny12/kakoune,mawww/kakoune,jkonecny12/kakoune,Somasis/kakoune,alexherbo2/kakoune,occivink/kakoune,mawww/kakoune,casimir/kakoune,danr/kakoune,casimir/kakoune