Correct validator public key type

[ArtiomTr]

/// BLS public key - 52 bytes (as defined in lean spec)
#[derive(Clone, Debug, PartialEq, Eq, Ssz)]
#[ssz(transparent)]
pub struct BlsPublicKey(pub ByteVector<U52>);

So just to make clear - lean spec defines not BLS signatures, but XMSS. Second - if you're sure here are BLS signatures, then double-check size - as far as I remember, bls public keys are 48 bytes long, not 52.

Also, please avoid hardcoding everywhere 52. You can define type:

type PublicKeySize = U52;

And then use everywhere:

PublicKeySize::USIZE

Instead of hardcoded constant 52.