Update EIP-4675: Fix SPDX license identifier (ethereum#5231)

* Fix SPDX license identifier in EIP-4675

* Satisfy eth bot

* Delete SafeMath.sol

EIPS/eip-4675.md

@@ -209,4 +209,5 @@ If an arbitrary account has the right to call `setParentNFT()` there might be a
 To prevent this issue, implementors should just allow **admin** to call, or fractionalize and receive NFT in an atomic transaction similar to flash loan(swap).
 
 ## Copyright
+
 Copyright and related rights waived via [CC0](../LICENSE.md).

assets/eip-4675/contracts/ERC20Token.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: CC0-1.0
 pragma solidity ^0.8.0;
 
 import "./interface/IERC20.sol";

assets/eip-4675/contracts/MFNFT.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: CC0-1.0
 pragma solidity ^0.8.0;
 
 import "./interface/IMFNFT.sol";

assets/eip-4675/contracts/NFT.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: MIT
+// SPDX-License-Identifier: CC0-1.0
 pragma solidity ^0.8.0;
 
 import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

assets/eip-4675/contracts/helper/Verifier.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: ISC
+// SPDX-License-Identifier: CC0-1.0
 pragma solidity ^0.8.0;
 
 contract Verifier {

assets/eip-4675/contracts/interface/IERC20.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: ISC
+// SPDX-License-Identifier: CC0-1.0
 pragma solidity ^0.8.0;
 
 /**

assets/eip-4675/contracts/interface/IERC721.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: UNLICENSED
+// SPDX-License-Identifier: CC0-1.0
 pragma solidity ^0.8.0;
 
 /**

assets/eip-4675/contracts/interface/IMFNFT.sol

@@ -1,4 +1,4 @@
-// SPDX-License-Identifier: ISC
+// SPDX-License-Identifier: CC0-1.0
 pragma solidity ^0.8.0;
 
 interface IMFNFT {

assets/eip-4675/package.json

@@ -12,7 +12,7 @@
   },
   "keywords": [],
   "author": "",
-  "license": "ISC",
+  "license": "CC0-1.0",
   "bugs": {
     "url": "https://github.com/PowerStream3604/multi-fnft/issues"
   },