Update vertex_ai_firebase_flutter_app/README.md

Co-authored-by: Parker Lougheed <[email protected]>

Author: domesticmouse

vertex_ai_firebase_flutter_app/README.md

@@ -70,7 +70,7 @@ The application features platform-optimized layouts:
   - Tool calls and responses visualization
   - Formatted log entries for debugging
 
-### Mobile Layout (Tabbed)
+### Mobile layout (tabbed)
 
 Same as above, but laid out as two tabs instead of side by side.
 Various adaptions to mobile to make things easier for finger interactions.