Merge branch '22820-api-use-env-not-request-in-helpers' into 'master'

Resolve "NameError: undefined local variable or method `request' for #<Grape::Middleware::Error:0x007fc990..."

## What does this MR do?

Switches from `request` to `env` in an API helper method as the helpers are included in contexts lacking `request`.

## Are there points in the code the reviewer needs to double check?

I couldn't build a reproducer for this.

Closes #22820

See merge request !6615

lib/api/helpers.rb

@@ -25,7 +25,7 @@ module API
     # Until CSRF protection is added to the API, disallow this method for
     # state-changing endpoints
     def find_user_from_warden
-      warden.try(:authenticate) if request.get? || request.head?
+      warden.try(:authenticate) if %w[GET HEAD].include?(env['REQUEST_METHOD'])
     end
 
     def find_user_by_private_token