fix(issue-details): Remove dead white color from close button

The color was copied from replay panel which has a dark background.
This banner uses a light background and the icon already uses
variant="muted", so the white color rule was unused.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: romtsn

static/app/components/events/interfaces/crashContent/exception/androidNativeTombstonesBanner.tsx

@@ -242,7 +242,6 @@ const CloseDropdownMenu = styled(DropdownMenu)`
   display: block;
   top: ${p => p.theme.space.md};
   right: ${p => p.theme.space.md};
-  color: ${p => p.theme.colors.white};
   cursor: pointer;
   z-index: 1;
 `;