DEV: Remove bulk group admin endpoints (#11949)

Originally added in 47e25648df. Looks like all related code was removed in c82b2dcc24 and b76731d722.

spec/requests/admin/groups_controller_spec.rb

@@ -237,44 +237,6 @@ RSpec.describe Admin::GroupsController do
     end
   end
 
-  describe "#bulk_perform" do
-    fab!(:group) do
-      Fabricate(:group,
-        name: "test",
-        primary_group: true,
-        title: 'WAT',
-        grant_trust_level: 3
-      )
-    end
-
-    fab!(:user) { Fabricate(:user, trust_level: 2) }
-    fab!(:user2) { Fabricate(:user, trust_level: 4) }
-
-    it "can assign users to a group by email or username" do
-      Jobs.run_immediately!
-
-      put "/admin/groups/bulk.json", params: {
-        group_id: group.id, users: [user.username.upcase, user2.email, 'doesnt_exist']
-      }
-
-      expect(response.status).to eq(200)
-
-      user.reload
-      expect(user.primary_group).to eq(group)
-      expect(user.title).to eq("WAT")
-      expect(user.trust_level).to eq(3)
-
-      user2.reload
-      expect(user2.primary_group).to eq(group)
-      expect(user2.title).to eq("WAT")
-      expect(user2.trust_level).to eq(4)
-
-      json = response.parsed_body
-      expect(json['message']).to eq("2 users have been added to the group.")
-      expect(json['users_not_added'][0]).to eq("doesnt_exist")
-    end
-  end
-
   context "#destroy" do
     it 'should return the right response for an invalid group_id' do
       max_id = Group.maximum(:id).to_i