Describe the bug
Quote and Pullquote use the HTML5 <cite> element to indicate who made the quote, as illustrated by the previews. The HTML Living Standard says this is not allowed.

To reproduce
Steps to reproduce the behavior:

1. Create a post
2. Add a Quote or Pullquote block
3. Fill in the Quote or Pullquote fields
4. Publish the post
5. View the post
6. Inspect the Quote or Pullquote

Expected behavior
Quote and Pullquote are valid HTML. This can be achieved by replacing the <cite> element with another HTML element, for instance the <footer> element as illustrated by the Mozilla Developer Network.