Remove a couple of unused `<annotation>` inputs

The `annotation` component does not declare `isSidebar` or `isLastReply`
in its bindings so these properties are unused.

src/sidebar/templates/annotation_thread.html

@@ -16,8 +16,6 @@
     <annotation ng-class="vm.annotationClasses()"
              annotation="vm.thread.annotation"
              is-collapsed="vm.thread.collapsed"
-             is-last-reply="$last"
-             is-sidebar="::vm.isSidebar"
              name="annotation"
              ng-mouseenter="vm.annotationHovered = true"
              ng-mouseleave="vm.annotationHovered = false"