Remove unused template, SASS for old `AnnotationHeader` Angular component

src/sidebar/templates/annotation-header.html

-<header class="annotation-header">
-  <!-- User -->
-  <span ng-if="vm.user()">
-    <annotation-user annotation="vm.annotation"></annotation-user>
-    <span class="annotation-collapsed-replies">
-      <a class="annotation-link" href=""
-        ng-click="vm.onReplyCountClick()"
-        ng-pluralize count="vm.replyCount"
-        when="{'0': '', 'one': '1 reply', 'other': '{} replies'}"></a>
-    </span>
-    <br />
-    <span class="annotation-header__share-info">
-      <a class="annotation-header__group"
-        target="_blank" ng-if="vm.group() && vm.group().links.html" href="{{vm.group().links.html}}">
-        <i class="h-icon-group"></i><span class="annotation-header__group-name">{{vm.group().name}}</span>
-      </a>
-      <span ng-show="vm.isPrivate"
-        title="This annotation is visible only to you.">
-        <i class="h-icon-lock"></i><span class="annotation-header__group-name" ng-show="!vm.group().links.html">Only me</span>
-      </span>
-      <i class="h-icon-border-color" ng-show="vm.isHighlight && !vm.isEditing" title="This is a highlight. Click 'edit' to add a note or tag."></i>
-      <span ng-if="::vm.showDocumentInfo">
-        <span class="annotation-citation" ng-if="vm.documentMeta().titleLink">
-          on "<a ng-href="{{vm.documentMeta().titleLink}}">{{vm.documentMeta().titleText}}</a>"
-        </span>
-        <span class="annotation-citation" ng-if="!vm.documentMeta().titleLink">
-          on "{{vm.documentMeta().titleText}}"
-        </span>
-        <span class="annotation-citation-domain"
-              ng-if="vm.documentMeta().domain">({{vm.documentMeta().domain}})</span>
-      </span>
-    </span>
-  </span>
-
-  <span class="u-flex-spacer"></span>
-
-  <timestamp
-    class-name="'annotation-header__timestamp'"
-    timestamp="vm.updated()"
-    href="vm.htmlLink()"
-    ng-if="!vm.editing() && vm.updated()"></timestamp>
-</header>

src/styles/sidebar/components/annotation.scss

@@ -3,7 +3,6 @@
 // Highlight quote of annotation whenever its thread is hovered
 .thread-list__card:hover .annotation-quote {
   border-left: $highlight 3px solid;
-  color: $grey-5;
 }
 
 // When hovering a top-level annotation, show the footer in a hovered state.
@@ -60,35 +59,10 @@
 }
 
 .annotation-quote-list,
-.annotation-header,
 .annotation-footer {
   @include pie-clearfix;
 }
 
-.annotation-header {
-  display: flex;
-  flex-direction: row;
-  align-items: baseline;
-  // Margin between top of x-height of username and
-  // top of the annotation card should be ~15px
-  margin-top: -$layout-h-margin + 10px;
-}
-
-.annotation-header__share-info {
-  color: $grey-5;
-  @include font-normal;
-}
-
-.annotation-header__group {
-  color: $color-gray;
-  font-size: $body1-font-size;
-}
-
-.annotation-header__group-name {
-  display: inline-block;
-  margin-left: 5px;
-}
-
 .annotation-body {
   @include font-normal;
   color: $grey-6;
@@ -164,11 +138,6 @@
   color: $grey-5;
 }
 
-.annotation-header__timestamp {
-  @include font-small;
-  color: $grey-4;
-}
-
 .annotation-actions {
   float: right;
   margin-top: 0;