Decouple UserMenu and SortMenu styling from TopBar

Remove unused `TopBar` SASS module.

src/sidebar/components/SortMenu.js

@@ -28,8 +28,8 @@ export default function SortMenu() {
   });
 
   const menuLabel = (
-    <span className="TopBar__menu-label">
-      <Icon name="sort" classes="TopBar__menu-icon" />
+    <span className="p-1">
+      <Icon name="sort" />
     </span>
   );
 

src/sidebar/components/UserMenu.js

@@ -87,8 +87,8 @@ function UserMenu({ auth, frameSync, onLogout, settings }) {
   })();
 
   const menuLabel = (
-    <span className="TopBar__menu-label">
-      <Icon name="profile" classes="TopBar__menu-icon" />
+    <span className="p-1">
+      <Icon name="profile" />
     </span>
   );
   return (

src/styles/sidebar/components/TopBar.scss

-@use '../../variables' as var;
-
-.TopBar {
-  // FIXME This is used by SortMenu and UserMenu.
-  &__menu-label {
-    padding: var.$layout-space--xxsmall;
-  }
-}

src/styles/sidebar/components/_index.scss

@@ -29,7 +29,6 @@
 @use './ThreadCard';
 @use './ThreadList';
 @use './ToastMessages';
-@use './TopBar';
 @use './VersionInfo';
 
 // TODO: Put these in @layer components after shared component styles have