grafana: add instance to flow control metrics legend (#10749)
grafana: add instance to flow control metrics legend (#10749)

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

Co-authored-by: Ti Chi Robot <040e6455cde1c91e876ec337e785ce913eacba35@tidb.io>
BusyJay/tikv,BusyJay/tikv,BusyJay/tikv,BusyJay/tikv