[0.9.39] Configure SetMembers for collectives pallet.

[hbulgarini]

As part of the release 0.9.39 (PR paritytech/substrate#13159), now the origin to add a new members in a collective can be configured from the runtime.

// Origin allowed to set collective members
		type SetMembersOrigin: EnsureOrigin<<Self as frame_system::Config>::RuntimeOrigin>;

When trappist gets upgraded to 0.9.39 release, this has to be configured with Root origin.

parameter_types! {
		/// Origin allowed to set collective members
		type SetMembersOrigin: EnsureOrigin<<Self as frame_system::Config>::RuntimeOrigin>;
}