Update 422 page styling

What does this MR do and why?

Describe in detail what your merge request does and why.

Update 422 page styling

• update buttons to pajamas
• use standard styling

Changelog: changed

Screenshots or screen recordings

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

How to reproduce

1. Register a new user on GitLab
2. Register a new user on GitHub with the same email from previous step
3. Goto sign up page on GitLab
4. Click on GitHub button
5. You should see the omniauth_error page as the same as before

OR

1. Implement the following patch

diff --git a/ee/app/controllers/groups/security/policies_controller.rb b/ee/app/controllers/groups/security/policies_controller.rb
index 3cd72f6a5bcc..4fa70780d4b9 100644
--- a/ee/app/controllers/groups/security/policies_controller.rb
+++ b/ee/app/controllers/groups/security/policies_controller.rb
@@ -25,7 +25,11 @@ def edit
       end
 
       def index
-        render :index, locals: { group: group }
+        # render :index, locals: { group: group }
+        @provider = 'Test Provider'
+
+        render 'errors/omniauth_error', layout: "oauth_error", status: :unprocessable_entity
       end
 
       def schema

1. Navigate to http://gdk.test:3443/groups/flightjs/-/security/policies

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #384424 (closed)