debian/control: Update package uploaders list. (Closes: #1069561)

Gunnar Hjalmarsson gunnarhj@debian.org has retired [1][2]. Please remove them from the Uploaders list of the package.

Thanks.

[1] https://nm.debian.org/person/gunnarhj/ [2] https://discourse.ubuntu.com/t/in-memoriam-gunnar-hjalmarsson/42284