Deduplicate the waitForPointerUp helper function in the highlight editor integration tests

The helper function is available in `test_utils.mjs` since commit
3fe55ba, so we can remove the local copy by importing it.

test/integration/highlight_editor_spec.mjs

@@ -16,7 +16,6 @@
 import {
   awaitPromise,
   closePages,
-  createPromise,
   getEditorSelector,
   getFirstSerialized,
   getRect,
@@ -37,6 +36,7 @@ import {
   unselectEditor,
   waitAndClick,
   waitForAnnotationModeChanged,
+  waitForPointerUp,
   waitForSelectedEditor,
   waitForSerialized,
   waitForTimeout,
@@ -54,11 +54,6 @@ const selectAll = async page => {
   );
 };
 
-const waitForPointerUp = page =>
-  createPromise(page, resolve => {
-    window.addEventListener("pointerup", resolve, { once: true });
-  });
-
 const switchToHighlight = switchToEditor.bind(null, "Highlight");
 
 describe("Highlight Editor", () => {