Limit Geo LogCursor spec to run only on PostgreSQL

spec/lib/gitlab/geo/log_cursor/daemon_spec.rb

 require 'spec_helper'
 
-describe Gitlab::Geo::LogCursor::Daemon do
+describe Gitlab::Geo::LogCursor::Daemon, :postgresql do
   describe '#run!' do
     let!(:geo_node) { create(:geo_node, :current) }