archive.gplhost.com archive is debian only

Don't mention the existence of mirrors for this archive for other
distributions.

Change-Id: I6e70b73e61711eb04602402bcd40dd2f5890a8cd
backport: havana
(cherry picked from commit ee1a053fc39793830080805111882270fcc9cf0f)
Merge "archive.gplhost.com archive is debian only" into stable/havana