Use 198.51.100.0/24 addresses in Geo docs
I saw this MR in the omnibus project omnibus-gitlab!2980 (merged). It suggests to no longer use 1.1.1.1
addresses, but instead use TEST-NET-2 addresses in the 198.51.100.0/24
range.
We should do this for Geo too. It makes sense to have sensible addresses in the examples used in the Geo docs. We can use 198.51.100.1
for Geo primary nodes and 198.51.100.2
and following for secondary nodes.