Bug Report

What did you do?

Upgraded the client version so that the client side support GetClusterInfo.TsoUrls and FindGroupByKeyspaceID but the server side doesn't, then called GetTS().
Issue Number: Ref #5895

What did you expect to see?

Successfully fallback to the legacy path to discover the primary server of the default keyspace group.

What did you see instead?

Returned "FindGroupByKeyspaceID not implemented"

What version of PD are you using (pd-server -V)?

TiKV/master for tso microservice in cloud