Remove user bio placeholder
Remove user bio placeholder

Refs flarum/core#1214.

ogioncz/flarum-ext-czech,FlarumChina/flarum-ext-simplified-chinese-pro,FlarumChina/flarum-ext-simplified-chinese-pro,flarum/flarum-ext-english,ogioncz/flarum-ext-czech,flarum/english