Move productivity_analytics.scss into page bundle

There are no visual changes as a result of this
commit.

config/application.rb

@@ -189,6 +189,7 @@ module Gitlab
     config.assets.precompile << "page_bundles/milestone.css"
     config.assets.precompile << "page_bundles/pipeline.css"
     config.assets.precompile << "page_bundles/pipelines.css"
+    config.assets.precompile << "page_bundles/productivity_analytics.css"
     config.assets.precompile << "page_bundles/todos.css"
     config.assets.precompile << "page_bundles/reports.css"
     config.assets.precompile << "page_bundles/xterm.css"

ee/app/assets/stylesheets/pages/productivity_analytics.scss → ee/app/assets/stylesheets/page_bundles/productivity_analytics.scss

+@import 'page_bundles/mixins_and_variables_and_functions';
+
 .dropdown-container {
   flex: 0 0 25%;
   width: 25%;
@@ -121,7 +123,7 @@
 
   .mr-title {
     a {
-      color: $gl-text-color;
+      color: var(--gl-text-color, $gl-text-color);
     }
   }
 }

ee/app/views/groups/analytics/productivity_analytics/show.html.haml

 - page_title _('Productivity Analytics')
-
+- add_page_specific_style 'page_bundles/productivity_analytics'
 - data_attributes = @request_params.valid? ? @request_params.to_data_attributes : @request_params.to_default_data_attributes
 
 #js-productivity-analytics{ data: data_attributes.merge(hide_group_drop_down: 'true') }