add sequence update test

spec/mutations/sequences/update_spec.rb

@@ -6,4 +6,18 @@ describe Sequences::Update do
     evil_params = {sequence: theirs, device: you, name: "impossible", body: []}
     expect { K.run!(evil_params) }.to raise_error(Errors::Forbidden)
   end
+
+  it "updates sequence folder_id" do
+    device = FactoryBot.create(:device)
+    folder = Folder.create!(name: "My Folder",
+                            color: "green",
+                            device: device)
+    sequence = FakeSequence.create(device: device)
+    result = Sequences::Update.run!(sequence: sequence,
+                                    name: "My Sequence",
+                                    device: device,
+                                    folder_id: folder.id,
+                                    body: [])
+    expect(sequence.folder_id).to equal(folder.id)
+  end
 end