Fix counter sizing (mastodon#12446)

Counter size is currently set to strict 33.3% width, but with it
counter may break in other languages than English. For example it is
already broken on Gargron's profile on mastodon.social using Russian
locale.

This commit changes "width" to "min-width", so counters still displayed
correctly, but if they need more width to fit text, they are now allowed
to take as many width as they need.

app/javascript/styles/mastodon/containers.scss

@@ -646,7 +646,7 @@
         }
 
         .counter {
-          width: 33.3%;
+          min-width: 33.3%;
           box-sizing: border-box;
           flex: 0 0 auto;
           color: $darker-text-color;