Reformat escalus_stanza

Fix indentation after #xmlelement{} -> #xmlel{} rename.

Fix some non-Erlang style bracing patterns like:

    children = [#xmlel{
                   name = <<"body">>,
                   children = [exml:escape_cdata(Msg)]
                  }
               ]

instead of:

    children = [#xmlel{name = <<"body">>,
                       children = [exml:escape_cdata(Msg)]}]