d/gbp.conf: use byzantium branch

4 jobs for pureos/0.0.5-1pureos1 in 6 minutes and 16 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Package
passed #324179
librem5
package:deb-debian-buster

00:01:15

passed #324180
librem5:arm64
package:deb-debian-buster:arm64

00:04:23

 
  Test Package
passed #324181
librem5
autopkgtest-debian-buster-package

00:00:36

passed #324182
librem5
lintian-debian-buster-package

00:00:36