When I was creating an app to solve a problem, I investigated because there was a case where predictive conversion appeared when typing characters in the form and the answer was known in advance.
It seems that the predictive conversion disappears when the autocomplete attribute of is turned off.
autocomplete: 'off'
Predictive conversion is called autocomplete.
form.rb
<%= text_field_tag "word#{word.id}","", {class: 'form-control',autocomplete: 'off'} %>