Improve wrapping of bottom row of topic data

On small screens, when the bottom row with a topic's comments, source,
and age starts wrapping, there was some weird behavior. This improves it
so that:

* The number(s) for comments won't wrap separately
* If the row gets taller due to wrapping, text will align to the bottom

tildes/scss/modules/_topic.scss

@@ -233,16 +233,17 @@
 
   grid-column-gap: 0.4rem;
 
+  align-items: end;
   max-width: 32rem;
   white-space: nowrap;
 }
 
 .topic-info-comments {
   white-space: normal;
-}
 
-.topic-info-comments-new {
+  span {
     white-space: nowrap;
+  }
 }
 
 .topic-info-source {

tildes/tildes/templates/macros/topics.jinja2

@@ -80,7 +80,7 @@
 
           {% if request.user.open_new_tab_internal %}target="_blank"{% endif %}
         >
-          {{ pluralize(topic.num_comments, "comment") }}
+          <span>{{ pluralize(topic.num_comments, "comment") }}</span>
 
           {% if topic.comments_since_last_visit %}
             <span class="topic-info-comments-new" title="Last visit {{ topic.last_visit_time|ago }}">