Merge branch '18283-pluralize-stage-headings' into 'master'

Get rid of pluralize on stage names

## What does this MR do?
Removes `pluralize` from stage names

## What are the relevant issue numbers?
Closes #18283   
Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/18920

## Screenshots (if relevant)
![Screen_Shot_2016-07-06_at_11.11.39_AM](/uploads/b1b2dd00dc8aacc6dff40cab1fe1ecdd/Screen_Shot_2016-07-06_at_11.11.39_AM.png)

cc @ayufan 


See merge request !5117

app/views/projects/commit/_ci_stage.html.haml

@@ -7,7 +7,7 @@
         = ci_icon_for_status(status)
       - if stage
          
-        = stage.titleize.pluralize
+        = stage.titleize
   = render statuses.latest.ordered, coverage: @project.build_coverage_enabled?, stage: false, ref: false, allow_retry: true
   = render statuses.retried.ordered, coverage: @project.build_coverage_enabled?, stage: false, ref: false, retried: true
   %tr

app/views/projects/pipelines/index.html.haml

@@ -50,7 +50,7 @@
             - stages.each do |stage|
               %th.stage
                 %span.has-tooltip{ title: "#{stage.titleize}" }
-                  = stage.titleize.pluralize
+                  = stage.titleize
             %th Duration
             %th
           = render @pipelines, commit_sha: true, stage: true, allow_retry: true, stages: stages

spec/features/pipelines_spec.rb

@@ -123,7 +123,7 @@ describe "Pipelines" do
     before { visit namespace_project_pipeline_path(project.namespace, project, pipeline) }
 
     it 'showing a list of builds' do
-      expect(page).to have_content('Tests')
+      expect(page).to have_content('Test')
       expect(page).to have_content(@success.id)
       expect(page).to have_content('Deploy')
       expect(page).to have_content(@failed.id)