Remove mention of grouped-update key

Co-authored-by: Barry Gordon <896971+brrygrdn@users.noreply.github.com>

updater/spec/dependabot/api_client_spec.rb

@@ -175,13 +175,12 @@
     end
 
     context "grouped updates" do
-      it "does not include the grouped-update or dependency-group keys by default" do
+      it "does not include the dependency-group key by default" do
         client.create_pull_request(dependency_change, base_commit)
 
         expect(WebMock).
           to(have_requested(:post, create_pull_request_url).
              with do |req|
-               expect(req.body).not_to include("grouped-update")
                expect(req.body).not_to include("dependency-group")
              end)
       end