Simplify error handling in answer create method

We were previously catching all exceptions when creating the answer and returning a generic error.
As exception handling is done in `AjaxController`, we don't need to do this and can get more specific error messages instead.

app/controllers/ajax/answer_controller.rb

@@ -32,20 +32,11 @@ class Ajax::AnswerController < AjaxController
       return
     end
 
-    answer = nil
-
-    begin
     answer = if inbox
                inbox_entry.answer params[:answer], current_user
              else
                current_user.answer question, params[:answer]
              end
-    rescue => e
-      Sentry.capture_exception(e)
-      @response[:status] = :err
-      @response[:message] = I18n.t('messages.error')
-      return
-    end
 
     services = JSON.parse params[:share]
     services.each do |service|