Fix broken whitespace in redraft

This still doesn't, for example, reconstruct the markdown the author
may have used to format their post.

brutaldon/views.py

@@ -766,7 +766,7 @@ def redraft(request, id):
         toot_content = re.sub("(^\n)|(\n$)", "", re.sub("\n\n", "\n", toot_content))
         # Fix up references
         for mention in toot.mentions:
-            menchie_re = re.compile(r"\s?@" + mention.username + r"\s", re.I)
+            menchie_re = re.compile(r"\s?@\s" + mention.acct + r"\s", re.I)
             toot_content = menchie_re.sub(
                 " @" + mention.acct + " ", toot_content, count=1
             )