net-im/telegram-desktop: Chase Qt6 update

This unfortunately makes use of the Qt private API, so it has to be
rebuilt with each Qt update.

net-im/telegram-desktop/Makefile

 PORTNAME=	telegram-desktop
 DISTVERSION=	5.1.7
+PORTREVISION=	1
 CATEGORIES=	net-im
 MASTER_SITES=	https://github.com/${GH_ACCOUNT}/${GH_PROJECT}/releases/download/v${DISTVERSION}/
 DISTNAME=	tdesktop-${DISTVERSION}-full