docs: update readme

Author: syrosh

README.md

@@ -184,7 +184,6 @@ Rendered Markdown, such as data from GitLab issues, are only served from the `sr
 
 ## TODO
 
-- [ ] pdf viewer
 - [ ] watch for all blur events, prevent rocketchat takeover
 - [ ] when logged in as admin, show big big big message that you should logout
 - [ ] sidebar hide