package/x11r7/xserver_xorg-server: bump version to 1.20.6

Removed patches 0006 & 0007 which were applied upstream as single
commit on the server-1.20-branch branch:
https://gitlab.freedesktop.org/xorg/xserver/commit/07efd81b819f21046afc0bb7e19a6cdf7f3c7ea9



Updated upstream URL for patch 0001.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>