The YubiKey::save_object doesn't require mutable reference

[G1gg1L3s]

In the current version, the Yubikey::save_object method requires a mutable reference to the data being saved:

yubikey.rs/src/yubikey.rs

Lines 629 to 634 in b07612e

	/// Save an object.
	#[cfg(feature = "untested")]
	pub fn save_object(&mut self, object_id: ObjectId, indata: &mut [u8]) -> Result<()> {
	let txn = self.begin_transaction()?;
	txn.save_object(object_id, indata)
	}

However, it appears that the mutability requirement is unnecessary, given that the Transaction::save_object method accepts an immutable slice:

yubikey.rs/src/transaction.rs

Lines 486 to 488 in b07612e

	/// Save an object.
	pub fn save_object(&self, object_id: ObjectId, indata: &[u8]) -> Result<()> {
	let templ = [0, Ins::PutData.code(), 0x3f, 0xff];

I understand that this modification is currently marked under the untested feature. Nevertheless, moving to the use of an immutable slice would definitely enhance the API.