Remove hydra-cli

See
https://github.com/mjolnir-io/mjolnir/issues/412#issuecomment-52809215.
In short, Hydra is dead. It'll return as Mjolnir hopefully in the near
future, but Hydra-cli will see no further updates.

Closes #31739.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>