Unable to remove margin in Pullquote

[jameskoster]

The Pullquote block outputs a blockquote inside a figure. The issue is that the blockquote inherits a default margin, and since the editor does not allow you to target it specifically, it's not possible to remove that margin. Here's the result:

Ideally it should be possible to make the text of the pullquote align with the paragraph before and after it.

[t-hamano]

I've submitted #45731 to add spacing supports to the Pullquote block.

Once margins are controllable, the default margin for blockquote will no longer be necessary, so I've added a style to reset the default margin at the same time.