Remove some unused annotation-component CSS and simplify

src/sidebar/components/Annotation/Annotation.js

@@ -106,7 +106,7 @@ function Annotation({
             )}
             {isSaving && <div className="Annotation__actions">Saving...</div>}
             {showActions && (
-              <div className="Annotation__actions">
+              <div className="u-layout-row--justify-right u-stretch">
                 <AnnotationActionBar
                   annotation={annotation}
                   onReply={onReply}

src/sidebar/components/Annotation/AnnotationHeader.js

@@ -139,7 +139,7 @@ function AnnotationHeader({
         )}
 
         {showTimestamps && (
-          <div className="AnnotationHeader__timestamps">
+          <div className="u-layout-row--justify-right u-stretch">
             <AnnotationTimestamps
               annotationCreated={annotation.created}
               annotationUpdated={annotation.updated}

src/styles/sidebar/components/Annotation.scss

@@ -17,12 +17,4 @@
 
 .Annotation {
   @include layout.vertical-rhythm;
-
-  &__reply-toggle {
-    @include buttons.button--link;
-  }
-
-  &__actions {
-    margin-left: auto;
-  }
 }

src/styles/sidebar/components/AnnotationBody.scss

@@ -12,11 +12,4 @@
 .AnnotationBody__collapse-toggle {
   @include layout.row(right);
   @include layout.vertical-space(var.$layout-space--xsmall);
-
-  .AnnotationBody__collapse-toggle-button {
-    @include buttons.button--labeled;
-    // The button should not have a background color except when hovered/active:
-    // It should look like text only
-    background-color: transparent;
-  }
 }

src/styles/sidebar/components/AnnotationHeader.scss

@@ -16,12 +16,6 @@
     color: var.$color-text;
   }
 
-  // Timestamps are right aligned in a flex row
-  &__timestamps {
-    flex-grow: 1;
-    text-align: right;
-  }
-
   &__highlight-icon {
     @include utils.icon--small;
     color: var.$color-text--light;