Update gRPC to v1.6.0
golang.org/x/net/* libs also needed update, so they were set to 59a0b19b5533c7977ddeb86b017bf507ed407b12, the same revision used in Gitaly.
Edited by username-removed-367626
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
golang.org/x/net/* libs also needed update, so they were set to 59a0b19b5533c7977ddeb86b017bf507ed407b12, the same revision used in Gitaly.