Fix typo and method call arguments in wiki destroy endpoint

In this commit we fix a typo (`reponse` vs. `response`) and
also the method call `response_api_error!` that was lacking
one argument.

changelogs/unreleased/cwoolley-gitlab-master-patch-20932.yml

+---
+title: Fix bug in wiki page destroy API endpoint when an error is raised
+merge_request: 56285
+author:
+type: fixed

lib/api/wikis.rb

@@ -111,7 +111,7 @@ module API
           if response.success?
             no_content!
           else
-            render_api_error!(reponse.message)
+            unprocessable_entity!(response.message)
           end
         end
 

spec/requests/api/wikis_spec.rb

@@ -14,6 +14,7 @@ require 'spec_helper'
 
 RSpec.describe API::Wikis do
   include WorkhorseHelpers
+  include AfterNextHelpers
 
   let(:user) { create(:user) }
   let(:group) { create(:group).tap { |g| g.add_owner(user) } }
@@ -578,6 +579,20 @@ RSpec.describe API::Wikis do
           include_examples 'wiki API 404 Wiki Page Not Found'
         end
       end
+
+      context 'when there is an error deleting the page' do
+        it 'returns 422' do
+          project.add_maintainer(user)
+
+          allow_next(WikiPages::DestroyService, current_user: user, container: project)
+            .to receive(:execute).and_return(ServiceResponse.error(message: 'foo'))
+
+          delete(api(url, user))
+
+          expect(response).to have_gitlab_http_status(:unprocessable_entity)
+          expect(json_response['message']).to eq 'foo'
+        end
+      end
     end
 
     context 'when wiki belongs to a group project' do