help: Backed out changeset e99facd2cd2a, description of file urls

This help entry didn't try to describe the 'localhost' notation. It described a
non-standard host-less notation where 'local' just was the first part of a
sample relative path. It describe "urls" with relative and absolute paths like:

  file://file.txt
  file:///tmp/file.txt
  file://c:/tmp/file.txt

mercurial/help/urls.txt

@@ -1,7 +1,7 b''
 Valid URLs are of the form::
 
   local/filesystem/path[#revision]
-  file://localhost/filesystem/path[#revision]
+  file://local/filesystem/path[#revision]
   http://[user[:pass]@]host[:port]/[path][#revision]
   https://[user[:pass]@]host[:port]/[path][#revision]
   ssh://[user@]host[:port]/[path][#revision]