This field was added in [moby@5130fe5d38837302e], which
added it for use as intermediate struct when parsing CLI flags (through
`runconfig.ParseExec`) in [moby@c786a8ee5e9db8f5f].
Commit [moby@9d9dff3d0d9e92adf] rewrote the CLI to use
Cobra, and as part of this introduced a separate `execOptions` type in
`api/client/container`, however the ExecOptions.Detach field was still
used as intermediate field to store the flag's value.
Given that the client doesn't use this field, let's remove its use to
prevent giving the impression that it's used anywhere.
[moby@5130fe5d38837302e]: 5130fe5d38
[moby@c786a8ee5e9db8f5f]: c786a8ee5e
[moby@9d9dff3d0d9e92adf]: 9d9dff3d0d
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
50da0ad9df