IE11 - Cannot use backspace to delete an empty paragraph that follows another empty paragraph

[talldan]

Describe the bug
When in an empty paragraph in other browsers, backspace can be used to delete it, but not in internet explorer if the paragraph is after another paragraph

To reproduce
Steps to reproduce the behavior:

1. Go through complicated process to test editor in IE11
2. Create two empty paragraph blocks
3. Try using backspace to delete the second
4. Observe that paragraph isn't removed

Expected behavior
Paragraph is removed

Additional context

• Discovered on master at 713807d

[aduth]

This should be fixed as of #20594.

However, there's a separate issue which I've described at #20598.