Convert mattermost alert to pajamas

app/views/projects/mattermosts/_no_teams.html.haml

 - if @teams_error_message
   = content_for :flash_message do
-    .alert.alert-danger= @teams_error_message
+    .gl-alert.gl-alert-danger
+      = sprite_icon('error', css_class: 'gl-icon gl-alert-icon gl-alert-icon-no-title')
+      .gl-alert-body= @teams_error_message
 
 %p
   You aren’t a member of any team on the Mattermost instance at

changelogs/unreleased/233678-pajamas-mattermost-alert.yml

+---
+title: Convert mattermost alert to pajamas
+merge_request: 56556
+author:
+type: other

spec/features/projects/services/user_activates_mattermost_slash_command_spec.rb

@@ -113,7 +113,7 @@ RSpec.describe 'Set up Mattermost slash commands', :js do
 
         click_link 'Add to Mattermost'
 
-        expect(page).to have_selector('.alert')
+        expect(page).to have_selector('.gl-alert')
         expect(page).to have_content('test mattermost error message')
       end