Revert copy/paste mistake

The (<<+>>) operator was swapped for (<</>>) in c1bf93b to fix pcapriotti#360. This was
mistakenly reverted when implementing the new rendering logic for option
groups. This commit re-establishes the fix.

Author: tbidne

src/Options/Applicative/Help/Core.hs

@@ -230,7 +230,7 @@ optionsDesc global pprefs p = vsepChunks
     doc info opt = do
       guard . not . isEmpty $ n
       guard . not . isEmpty $ h
-      return (grp, (extractChunk n, align . extractChunk $ h <<+>> hdef))
+      return (grp, (extractChunk n, align . extractChunk $ h <</>> hdef))
       where
         (grp, n, _) = optDesc pprefs style info opt
         h = optHelp opt