package/weston: change download url to https

package/weston: change download url to https

- change download url to https (as given by the original announcement [1]
    and redirected by the http url)

Fixes:

  - http://autobuild.buildroot.net/results/00b9e1ccb97d9ff5c2ee0e856288f689bdab52ee

  >>> weston 9.0.0 Downloading[23m
  --2020-09-15 14:10:22--  http://wayland.freedesktop.org/releases/weston-9.0.0.tar.xz
  Resolving wayland.freedesktop.org (wayland.freedesktop.org)... 35.227.58.183
  Connecting to wayland.freedesktop.org (wayland.freedesktop.org)|35.227.58.183|:80... connected.
  HTTP request sent, awaiting response... 308 Permanent Redirect
  2020-09-15 14:10:23 ERROR 308: Permanent Redirect.

[1] https://lists.freedesktop.org/archives/wayland-devel/2020-September/041595.html

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>