Remove unnecessary variable

The variable was used only once and so there is no need for it to
exist. This way we save two lines of code and make the code a bit
simpler.

qa/qa/specs/features/browser_ui/2_plan/issue/collapse_comments_in_discussions_spec.rb

@@ -15,10 +15,8 @@ module QA
         issue.visit!
 
         Page::Project::Issue::Show.perform do |show|
-          my_first_discussion = 'My first discussion'
-
           show.select_all_activities_filter
-          show.start_discussion(my_first_discussion)
+          show.start_discussion('My first discussion')
           show.reply_to_discussion(my_first_reply)
         end
       end