Improve message about draft status

Let's use consistent wording in this UI message. We need to gradually
step away from the old WIP language in favor of 'draft'.

app/views/shared/issuable/form/_title.html.haml

@@ -5,7 +5,7 @@
 - div_class = no_issuable_templates ? 'col-sm-10' : 'col-sm-7 col-lg-8'
 - toggle_wip_link_start = '<a href="" class="js-toggle-wip">'
 - toggle_wip_link_end = '</a>'
-- add_wip_text = (_('%{link_start}Start the title with %{draft_snippet}%{link_end} to prevent a merge request that is a work in progress from being merged before it\'s ready.') % { link_start: toggle_wip_link_start, link_end: toggle_wip_link_end, draft_snippet: '<code>Draft:</code>'.html_safe } ).html_safe
+- add_wip_text = (_('%{link_start}Start the title with %{draft_snippet}%{link_end} to prevent a merge request draft from merging before it\'s ready.') % { link_start: toggle_wip_link_start, link_end: toggle_wip_link_end, draft_snippet: '<code>Draft:</code>'.html_safe } ).html_safe
 - remove_wip_text = (_('%{link_start}Remove the %{draft_snippet} prefix%{link_end} from the title to allow this merge request to be merged when it\'s ready.' ) % { link_start: toggle_wip_link_start, link_end: toggle_wip_link_end, draft_snippet: '<code>Draft</code>'.html_safe } ).html_safe
 
 %div{ class: div_class }

locale/gitlab.pot

@@ -717,7 +717,7 @@ msgstr ""
 msgid "%{link_start}Remove the %{draft_snippet} prefix%{link_end} from the title to allow this merge request to be merged when it's ready."
 msgstr ""
 
-msgid "%{link_start}Start the title with %{draft_snippet}%{link_end} to prevent a merge request that is a work in progress from being merged before it's ready."
+msgid "%{link_start}Start the title with %{draft_snippet}%{link_end} to prevent a merge request draft from merging before it's ready."
 msgstr ""
 
 msgid "%{link_start}What information does GitLab Inc. collect?%{link_end}"

spec/features/merge_request/user_sees_wip_help_message_spec.rb

@@ -46,8 +46,8 @@ RSpec.describe 'Merge request > User sees draft help message' do
           'It looks like you have some draft commits in this branch'
         )
         expect(page).to have_text(
-          "Start the title with Draft: to prevent a merge request that is a \
-work in progress from being merged before it's ready."
+          "Start the title with Draft: to prevent a merge request draft \
+from merging before it's ready."
         )
       end
     end