Remove documents and references to admin_legacy styling

.prettierignore

@@ -1,5 +1,4 @@
 app/assets/javascripts/vendor/
 app/assets/javascripts/admin_legacy
 app/assets/stylesheets/vendor/
-app/assets/stylesheets/admin_legacy
 spec/javascripts/admin_legacy

.stylelintrc.yml

@@ -1,4 +1,2 @@
 extends: stylelint-config-gds/scss
 ignoreFiles:
-  - app/assets/stylesheets/vendor/**/*
-  - app/assets/stylesheets/admin_legacy/**/*

app/assets/stylesheets/application.scss

@@ -15,7 +15,6 @@ $govuk-page-width: 1140px;
 @import "./components/summary-card";
 
 @import "./admin/overrides";
-@import "./admin/layout";
 
 @import "./admin/views/components/worldwide_offices/index/office-summary-card-component";
 
@@ -71,9 +70,3 @@ $govuk-page-width: 1140px;
     display: none;
   }
 }
-
-.legacy-whitehall {
-  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
-
-  @import "admin_legacy";
-}

docs/css.md

@@ -59,22 +59,6 @@ This folder will also store any `view_component` css.
 
 In this folder, all of the CSS for internal application components will be stored. The files should follow the same standards as the GOVUK Publishing Components and should be created in a way that can be ported over to the shared library.
 
-### Legacy CSS
-
-Legacy files will remain in the following folders structures:
-
-```
-- app
-  - assets
-    - stylesheets
-      - admin_legacy
-        - ...
-      - vendor
-      admin_legacy.scss
-```
-
-More details about legacy css standards can be found [here](/docs/legacy_css.md).
-
 ## Styles
 
 With the exception of namespaces, follow the [GOV.UK Frontend CSS conventions](https://github.com/alphagov/govuk-frontend/blob/main/docs/contributing/coding-standards/css.md), which describes in more detail our approach to namespaces, linting and BEM (block, element, modifier) CSS naming methodology.