What?

This is a follow-up to #42764 which fixed the position of the Next link on the first page of the Query loop to ensure that it's right aligned when the space between content justification is used.

An issue with the CSS from that PR is that when the parent Query Pagination block is selected in the block editor, then the block appender is the last element in the DOM under the Query Pagination block, so the :last-child rule does not wind up targeting the next link.

In this change, if we swap the :first-child rule to use a :last-of-type rule, it appears to fix the issue. Because the next link uses an a tag and the block appender uses a div tag, the updated rule correctly targets the last link under the parent Query pagination block.

Why?

Fix the display of the children of the Query pagination block when the block is selected in the editor.

How?

Update the rule the applies margin-inline-start: auto to the Query Pagination Next block to use :last-of-type instead of :last-child.

Testing Instructions

1. Add a Query Loop block with pagination
2. Select the Pagination block and set the content justification to space between
3. With this PR applied, the positioning of the Prev and Next buttons should look correct while the parent block is selected (see screenshots below)
4. Check that the issue fixed by Query Pagination: Correctly position the "next" link on the first page. #42764 is still fixed (when a Next block is the only block on the page, then it should be right aligned. One way to test this is to have your Query Pagination block only have Prev and Next blocks as children, then page through results on the site frontend)

Screenshots or screencast

Before	After