Make notification time smaller and reduce contrast (#9464)

app/javascript/styles/mastodon/components.scss

@@ -876,7 +876,8 @@
   }
 }
 
-.status__relative-time {
+.status__relative-time,
+.notification__relative_time {
   color: $dark-text-color;
   float: right;
   font-size: 14px;