Need to update rules

[qiffang]

replace_expr:
- rule_name: "pd_cluster_low_space"
expr: '(sum(pd_cluster_status{type="store_low_space_count"}) by (instance) > 0) and (sum(etcd_server_is_leader) by (instance) > 0)'
- rule_name: "pd_cluster_lost_connect_tikv_nums"
expr: '(sum ( pd_cluster_status{type="store_disconnected_count"} ) by (instance) > 0) and (sum(etcd_server_is_leader) by (instance) > 0)'
- rule_name: "pd_pending_peer_region_count"
expr: '(sum( pd_regions_status{type="pending_peer_region_count"} ) by (instance) > 100) and (sum(etcd_server_is_leader) by (instance) > 0)'