Make flash-alert background transparent to match flash-notice.

CHANGELOG

@@ -33,6 +33,7 @@ v 8.13.0 (unreleased)
   - Only update issuable labels if they have been changed
   - Take filters in account in issuable counters. !6496
   - Use custom Ruby images to test builds (registry.dev.gitlab.org/gitlab/gitlab-build-images:*)
+  - Prevent flash alert text from being obscured when container is fluid
   - Append issue template to existing description !6149 (Joseph Frazier)
   - Revoke button in Applications Settings underlines on hover.
   - Add missing values to linter !6276 (Katarzyna Kobierska Ula Budziszewska)

app/assets/stylesheets/framework/flash.scss

@@ -21,7 +21,8 @@
   .flash-notice, .flash-alert {
     border-radius: $border-radius-default;
 
-    .container-fluid.container-limited.flash-text {
+    .container-fluid,
+    .container-fluid.container-limited {
       background: transparent;
     }
   }
@@ -35,12 +36,6 @@
   }
 }
 
-.content-wrapper {
-  .flash-notice .container-fluid {
-    background-color: transparent;
-  }
-}
-
 @media (max-width: $screen-md-min) {
   ul.notes {
     .flash-container.timeline-content {