Remove RLP encoding

[NumberFour8]

RLP encoding was for legacy compatibility with TS. It should be removed in 3.0.

See:

hoprnet/common/primitive-types/src/lib.rs

Lines 13 to 16 in cfd705e

	// TODO: remove in 3.0
	// #[deprecated(note = "RLP encoding will be removed in 3.0")]
	/// Obsolete RLP encoding module to be removed in future versions.
	pub mod rlp {

and

hoprnet/common/primitive-types/Cargo.toml

Line 18 in cfd705e

rlp = "0.5.2" # TODO: remove in 3.0