Merge branch 'jivanvl-replace-alert-ci-variables' into 'master'

Replace alert class with gl-alert in ci_variables

See merge request gitlab-org/gitlab!44634

app/views/ci/variables/_index.html.haml

@@ -24,7 +24,7 @@
 - else
   .row
     .col-lg-12.js-ci-variable-list-section{ data: { save_endpoint: save_endpoint, maskable_regex: ci_variable_maskable_regex } }
-      .hide.alert.alert-danger.js-ci-variable-error-box
+      .hide.gl-alert.gl-alert-danger.js-ci-variable-error-box
 
       %ul.ci-variable-list
         = render 'ci/variables/variable_header'