Upgrade Gitaly dependency for new gRPC client keep alive policy
Relates to gitaly#1718 (closed)
Workhorse should upgrade the version of Gitaly to one that includes the change in gitaly!1294 (merged) so that the gRPC client to Gitaly uses keep alive pings to more aggressively detect bad connections and redial sooner.
Blocked until a tagged release of Gitaly is made with the change.