Fix old link in Gerrit Dashboards
Fix old link in Gerrit Dashboards

In the Tacker Contribution guide, Gerrit Dashboards refers to an
old link for dashboard link generation.

This patch replaces the old link [1] with the new link [2].

[1] https://github.com/openstack-archive/gerrit-dash-creator
[2] https://opendev.org/x/gerrit-dash-creator

Closes-Bug: #1934178
Change-Id: I9e6dd96e6e34f339591ac623243611618cc7a4f6

openstack/tacker,stackforge/tacker,openstack/tacker,stackforge/tacker,openstack/tacker