replatform: posts do not properly link to feed

[cantsin]

We should be linking to feed.xml directly. /feed/index.html is blank.

Sample file:

--- original/2014/03/31/announcing-fbopen-government-opportunities-made-easier/index.html	2024-08-09 08:24:37.430213177 -0700
+++ changed/2014/03/31/announcing-fbopen-government-opportunities-made-easier/index.html	2024-08-09 08:21:19.559152169 -0700

         <li class="margin-bottom-2">
-         <a class="usa-link--alt" href="/feed.xml">
+         <a class="usa-link--alt" href="/feed/">
           <img alt="" class="maxw-3 margin-right-2 text-sub" src=""/>
           RSS feed
          </a>