Replace at-/de-tached with dis-connectedCallback

attached() and detached() are Polymer 1 legacy.

Change-Id: Ic86d07bfb95ec316880db261a913004f5a6e5a22
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
index 3d6383b..267ca5f 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
@@ -970,7 +970,7 @@
   suite('create-comment', () => {
     setup(async () => {
       loggedIn = true;
-      element.attached();
+      element.connectedCallback();
       await flush();
     });