cover: tweak styles:

- `optimizeQuality` > `smooth` (CSS language evolution)
- Use `auto` instead of a fixed width.
- Add exceptions for heights and apply them to some previously modified templates.
- Remove `is-large` exception.
- Widen the content column on list curation.

bookwyrm/templates/discover/large-book.html

@@ -8,7 +8,7 @@
             <div class="column">
                 <a
                     href="{{ book.local_path }}"
-                >{% include 'snippets/book_cover.html' with cover_class='is-large' %}</a>
+                >{% include 'snippets/book_cover.html' %}</a>
 
                 {% include 'snippets/stars.html' with rating=book|rating:request.user %}
             </div>

bookwyrm/templates/discover/small-book.html

@@ -6,7 +6,7 @@
     {% with book=book %}
         <a
             href="{{ book.local_path }}"
-        >{% include 'snippets/book_cover.html' with cover_class='is-small' %}</a>
+        >{% include 'snippets/book_cover.html' with cover_class='is-h-small' %}</a>
 
         {% include 'snippets/stars.html' with rating=book|rating:request.user %}