Update seastar submodule
Update seastar submodule

* seastar eaa00e761f...8ed9771ae9 (5):
  > *: drop prometheus protobuf support
  > reactor: Fix calculations of bandwidth in legacy mode
  > gate: add gate::holder
  > Revert "gate: add gate::holder", does not build.
  > gate: add gate::holder

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla