net-im/telepathy-qt[45]: Fixup DOCSDIR, sipmlify -qt5

In r423332 DOCSDIR was defined incorrectly. Correct this.
While here, also remove PORTSDIR from the qt5 version as
suggested by Jan.

Thanks to Jan for spotting it.

Reported by: Jan Beich <jbeich@freebsd.org>
Reviewed by: jbeich, rakuco
Approved by: rakuco (mentor)
Differential Revision: https://reviews.freebsd.org/D7898