Simplify styles in `Annotation`

src/sidebar/components/Annotation/Annotation.js

@@ -60,7 +60,7 @@ function Annotation({
 
   return (
     <article
-      className={classnames('Annotation', {
+      className={classnames('Annotation', 'hyp-u-vertical-spacing', {
         'Annotation--missing': !annotation,
         'Annotation--reply': isReply,
         'is-collapsed': threadIsCollapsed,

src/styles/sidebar/components/Annotation.scss

-@use '../../mixins/buttons';
-@use '../../mixins/layout';
-@use '../../variables' as var;
-
-// When hovering a top-level annotation, show the footer in a hovered state.
-// When hovering a reply (at any level), show the reply's own footer in
-// a hovered state and also the footer of the top-level annotation.
-// TODO: Make these work again or remove
-.ThreadList__card:hover > .Annotation,
-.Annotation:hover {
-  .Annotation-replies__link,
-  .Annotation-replies__count,
-  .Annotation-action-btn {
-    color: var.$grey-6;
-  }
-}
-
-.Annotation {
-  @include layout.vertical-rhythm;
-}

src/styles/sidebar/sidebar.scss

@@ -18,7 +18,6 @@
 
 // Components
 // ----------
-@use './components/Annotation';
 @use './components/AnnotationPublishControl';
 @use './components/AnnotationShareControl';
 @use './components/AutocompleteList';