Copy changes around registering runners (#10244)

app/views/projects/runners/_group_runners.html.haml

@@ -21,7 +21,7 @@
   This group does not provide any group Runners yet.
 
   - if can?(current_user, :admin_pipeline, @project.group)
-    You can register group runners in the
+    Group masters can register group runners in the
     = link_to 'Group CI/CD settings', group_settings_ci_cd_path(@project.group)
   - else
     Ask your group master to setup a group Runner.

app/views/projects/runners/_shared_runners.html.haml

@@ -17,8 +17,8 @@
     for this project
 
 - if @shared_runners_count.zero?
-  This GitLab server does not provide any shared Runners yet.
-  Please use the specific Runners or ask your administrator to create one.
+  This GitLab instance does not provide any shared Runners yet. Instance
+  administrators can register shared Runners in the admin area.
 - else
   %h4.underlined-title Available shared Runners : #{@shared_runners_count}
   %ul.bordered-list.available-shared-runners