Bug: Drag handle test snapshot is incorrect for Firefox

[matthewlipski]

One of the tests for the drag handle involves creating a heading using the slash menu, then adding another through the drag handle:

test("Clicking add button should create new block", async () => {
  await executeSlashCommand(page, "h1");
  await page.keyboard.type("Hover over this text");
  await hoverAndAddBlockFromDragHandle(page, H_ONE_BLOCK_SELECTOR, "h2");
  await page.keyboard.type("This is an h2");
  await page.waitForSelector(H_TWO_BLOCK_SELECTOR);

  await page.waitForTimeout(1000);
  await compareDocToSnapshot(page, "draghandleadd");
});

However, running the test on Firefox adds an empty nested paragraph to the second heading, as can be seen when comparing the Firefox, Chromium, and Webkit snapshots. Since the reference snapshot includes this bug, the test still passes, though this should be changed such that Firefox behaviour is the same as Chromium and Webkit,

[matthewlipski]

A possibly related issue also arises for block drag & drop tests, for which Firefox behaviour is also drastically different to Chromium and Webkit.

[YousefED]

afaik this is documented in the codebase. It doesn't cause critical end-user bugs and tests on chromium still work.

Closing in favor of a cleaned backlog