assistant: Adjust slash command popover padding (#16181)

I've looked for other instances of the popover component where this change could cause a spacing regression but couldn't find any yet. Let me know if you do! Intuitively, I wouldn't change this padding directly on the component container, but I didn't find any other way to tackle it.

Release Notes:

- N/A

crates/ui/src/components/popover.rs

@@ -43,7 +43,7 @@ impl RenderOnce for Popover {
         div()
             .flex()
             .gap_1()
-            .child(v_flex().elevation_2(cx).px_1().children(self.children))
+            .child(v_flex().elevation_2(cx).py_1().children(self.children))
             .when_some(self.aside, |this, aside| {
                 this.child(
                     v_flex()