Style files "Show More" button border to match inside of table row

making the bottom border for the last table row item the same color as the inside of the table row

The following discussion from !39788 (merged) should be addressed:

I only discovered one tiny thing: On hover, the bottom border is actually inside of the table row, making the bottom border for the last item look bigger than all other ones. When comparing this with production however, I noticed that this is yet another bug that's already in our codebase 😆

Production	MR

This is definitely not blocking this MR, and we should probably push this to yet another issue/MR, but what do you think about this alternative of making the bottom border for the last table row item the same color as the inside of the table row to create this outcome?

Before	After