Fix ERC20._update (#3921)

Co-authored-by: Francisco <frangio.1@gmail.com>
Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>

test/token/ERC20/extensions/ERC20FlashMint.test.js

@@ -82,7 +82,7 @@ contract('ERC20FlashMint', function (accounts) {
       const data = this.token.contract.methods.transfer(other, 10).encodeABI();
       await expectRevert(
         this.token.flashLoan(receiver.address, this.token.address, loanAmount, data),
-        'ERC20: burn amount exceeds balance',
+        'ERC20: transfer amount exceeds balance',
       );
     });