refactor: remove protocol fee checks in MerkleStreamerLL

[smol-ninja]

Closes #256

Description

This PR removes protocol fee checks in MerkleStreamerLL and allows claiming even when the protocol fee is greater than 0. When $protocolFee>0$ then ${claimAmount}=(amount - protocolFee)$.

Changes

• SablierV2MerkleStreamer.sol - Removes protocol fee checks in _checkClaim and clawback.
• Errors.sol - Removes SablierV2MerkleStreamer_ProtocolFeeNotZero.

Testing

• claim.t.sol: Removes test_RevertGiven_ProtocolFeeNotZero and adds test_Claim_ProtocolFeeNotZero.
• clawback.t.sol: Removes modifiers givenProtocolFeeZero and givenProtocolFeeNotZero as clawback does not check for protocol fee anymore
• Updates branching trees.

Related: https://github.com/sablier-labs/company-discussions/discussions/28

[andreivladbrg]

LOCKUP is no longer used in abstract contract MerkleStreamer, thus it should be removed

v2-periphery/src/abstracts/SablierV2MerkleStreamer.sol

Lines 37 to 38 in 566deba

	/// @inheritdoc ISablierV2MerkleStreamer
	ISablierV2Lockup public immutable override LOCKUP;

This PR should have basically undo the changes made here: #220

[PaulRBerg]

That's a beautiful PR body message, thanks for the detailed report, @smol-ninja.

Feedback below.

[andreivladbrg]

@smol-ninja pushed a new commit, can you double check that the PR looks good now?

[smol-ninja]

Thanks Andrei for the commit. I didn't notice those Notes in the interface file. Looks good to me now.