Make it clear the license overusage is visible only to admins

Closes #607

CHANGELOG-EE

@@ -3,6 +3,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 v 8.9.0 (unreleased)
 
 v 8.8.3
+  - Make it clear the license overusage is visible only to admins
   - Reduce load on DB for license upgrade check
 
 v 8.8.2

app/helpers/license_helper.rb

@@ -72,7 +72,7 @@ module LicenseHelper
       message << "users, but it looks like your site has grown to"
       message << "#{current_active_user_count} users. Please contact"
       message << "sales@gitlab.com to increase the seats on your license."
-      message << "Thank you for choosing GitLab."
+      message << "Note: This message is only visible to you as an admin."
     end
 
     message.join(" ")

spec/helpers/license_helper_spec.rb

@@ -35,7 +35,7 @@ describe LicenseHelper do
         allow(license).to receive(:restrictions).and_return({ active_user_count: 50 })
         allow(User).to receive(:active).and_return(Array.new(100))
 
-        warn_msg = 'Your GitLab license currently covers 50 users, but it looks like your site has grown to 100 users. Please contact sales@gitlab.com to increase the seats on your license. Thank you for choosing GitLab.'
+        warn_msg = 'Your GitLab license currently covers 50 users, but it looks like your site has grown to 100 users. Please contact sales@gitlab.com to increase the seats on your license. Note: This message is only visible to you as an admin.'
         expect(license_message(signed_in: true, is_admin: true)).to eq(warn_msg)
       end
     end