GitHub: link to a faster landing page in GerritHub
GitHub: link to a faster landing page in GerritHub

The dashboards have changed in Gerrit 3.4 which got deployed to
GerritHub earlier today. Now there's no pagination and no is:mergeable
operator. Let's just link to a (paginated) list of all open changes,
that's probably better value for now.

Change-Id: I22ad68becfc33d3829bcd8aaccb5203e76faeded

Telecominfraproject/gnpy