[Doc] Update 5.0 to 5.1: Recompile assets

Recompiling assets on the update is needed or main menu appearance may not load properly. This has been mentioned on issues #3722 and #3978.

The command has been tested several by users on those issues and by myself.

Thanks for your time and attention.

doc/update/5.0-to-5.1.md

@@ -41,6 +41,7 @@ sudo -u git -H cp config/puma.rb.example config/puma.rb
 sudo -u git -H bundle install --without development test postgres --deployment
 sudo -u git -H bundle exec rake db:migrate RAILS_ENV=production
 sudo -u git -H bundle exec rake migrate_merge_requests RAILS_ENV=production
+sudo -u git -H bundle exec rake assets:precompile RAILS_ENV=production
 ```
 
 ### 5. Update init.d script with a new one