UI: User menu style fix (#29066)

## For #27609 

<img width="180" alt="Screenshot 2025-05-12 at 4 00 52 PM"
src="https://github.com/user-attachments/assets/1aabd897-ecae-45f0-9b53-c81677a47d55"
/>

- [x] Changes file added for user-visible changes in `changes/`
- [x] Manual QA for all new/changed functionality

---------

Co-authored-by: Jacob Shandling <jacob@fleetdm.com>

changes/27609-user-menu-style

@@ -0,0 +1 @@
+- Fix slight style issues with the user menu

frontend/components/top_nav/UserMenu/UserMenu.tsx

@@ -237,9 +237,6 @@ const UserMenu = ({
       "&:active": {
         backgroundColor: COLORS["ui-vibrant-blue-25"],
       },
-      "&:last-child, &:nth-last-of-type(2)": {
-        borderTop: `1px solid ${COLORS["ui-fleet-black-10"]}`,
-      },
     }),
   };