Remove blue background from social sign-in buttons

app/assets/stylesheets/utilities.scss

@@ -40,12 +40,12 @@
 
 // Classes using mixins coming from @gitlab-ui
 // can be removed once https://gitlab.com/gitlab-org/gitlab/merge_requests/19021 has been merged
-.gl-bg-blue-500 { @include gl-bg-blue-500; }
 .gl-bg-red-100 { @include gl-bg-red-100; }
 .gl-bg-orange-100 { @include gl-bg-orange-100; }
 .gl-bg-gray-100 { @include gl-bg-gray-100; }
 .gl-bg-green-100 { @include gl-bg-green-100;}
 
+.gl-text-blue-500 { @include gl-text-blue-500; }
 .gl-text-gray-900 { @include gl-text-gray-900; }
 .gl-text-red-700 { @include gl-text-red-700; }
 .gl-text-orange-700 { @include gl-text-orange-700; }

app/views/profiles/accounts/_providers.html.haml

@@ -16,6 +16,6 @@
             %a.provider-btn
               = s_('Profiles|Active')
         - elsif link_allowed
-          = link_to omniauth_authorize_path(:user, provider), method: :post, class: 'provider-btn gl-bg-blue-500' do
+          = link_to omniauth_authorize_path(:user, provider), method: :post, class: 'provider-btn gl-text-blue-500' do
             = s_('Profiles|Connect')
   = render_if_exists 'profiles/accounts/group_saml_unlink_buttons', group_saml_identities: group_saml_identities