d/control: Adjust maintainer and vcs fields

This is a PureOS only package atm
4 jobs for pureos/byzantium in 2 minutes and 42 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Package
passed #349587
librem5
package-pureos-byzantium

00:00:57

passed #349588
librem5:arm64
package-pureos-byzantium:arm64

00:02:42

 
  Test Package
passed #349589
librem5
autopkgtest-pureos-byzantium-package

00:01:19

passed #349590
librem5
lintian-pureos-byzantium-package

00:00:48