Update review app dropdown button padding

What does this MR do?

A tiny MVC for: https://gitlab.slack.com/archives/CETG54GQ0/p1620401583082300 where we remove the extra padding/margin for the deploy app button.

While we could do this upstream in gitlab/ui for all instances, we have opted for the most boring change possible here and just tackled this single instance.

Screenshots (strongly suggested)

Before	After

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.