Remove body_as_json in favor of built-in response.parsed_body for JSON response specs (#31749)

spec/requests/api/v1/domain_blocks_spec.rb

@@ -26,7 +26,7 @@ RSpec.describe 'Domain blocks' do
       subject
 
       expect(response).to have_http_status(200)
-      expect(body_as_json).to match_array(blocked_domains)
+      expect(response.parsed_body).to match_array(blocked_domains)
     end
 
     context 'with limit param' do
@@ -35,7 +35,7 @@ RSpec.describe 'Domain blocks' do
       it 'returns only the requested number of blocked domains' do
         subject
 
-        expect(body_as_json.size).to eq(params[:limit])
+        expect(response.parsed_body.size).to eq(params[:limit])
       end
     end
   end