Remove unused light-client leftover

[skunert]

Remove some leftover light-client code.

SyncingEngine instantiated here:

substrate/client/service/src/builder.rs

Line 830 in 91e0d66

Roles::from(&config.role),

Can not be light client :

substrate/client/network/common/src/role.rs

Lines 100 to 107 in 91e0d66

	impl<'a> From<&'a Role> for Roles {
	fn from(roles: &'a Role) -> Self {
	match roles {
	Role::Full => Self::FULL,
	Role::Authority => Self::AUTHORITY,
	}
	}
	}