Update comments in SignatureVerifierMuxer to reflect correct byte ran…

…ges for encodeData and payload lengths (#873)

This pull request includes modifying the `SignatureVerifierMuxer`
contract to correct the byte offsets for encoding and payload data.

Changes to byte offsets:

*
[`contracts/handler/extensible/SignatureVerifierMuxer.sol`](diffhunk://#diff-62f21ce8850527f34ef2acdacd96d4a2a1150e3e2a7e16457e82236bbd4259d2L124-R127):
Updated the byte offset ranges for `encodeData length`, `encodeData`,
and `payload length` to correct values.

contracts/handler/extensible/SignatureVerifierMuxer.sol

@@ -118,13 +118,13 @@ abstract contract SignatureVerifierMuxer is ExtensibleBase, ERC1271, ISignatureV
             if (sigSelector == SAFE_SIGNATURE_MAGIC_VALUE && signature.length >= 68) {
                 // Signature is for an `ISafeSignatureVerifier` - decode the signature.
                 // Layout of the `signature`:
-                // 0x00 - 0x04: selector
-                // 0x04 - 0x36: domainSeparator
-                // 0x36 - 0x68: typeHash
-                // 0x68 - 0x6C: encodeData length
-                // 0x6C - 0x6C + encodeData length: encodeData
-                // 0x6C + encodeData length - 0x6C + encodeData length + 0x20: payload length
-                // 0x6C + encodeData length + 0x20 - end: payload
+                // 0x00 to 0x04: selector
+                // 0x04 to 0x36: domainSeparator
+                // 0x36 to 0x68: typeHash
+                // 0x68 to 0x88: encodeData length
+                // 0x88 to 0x88 + encodeData length: encodeData
+                // 0x88 + encodeData length to 0x88 + encodeData length + 0x20: payload length
+                // 0x88 + encodeData length + 0x20 to end: payload
                 //
                 // Get the domainSeparator from the signature.
                 (bytes32 domainSeparator, bytes32 typeHash) = abi.decode(signature[4:68], (bytes32, bytes32));