Remove bad SafeCast test

test/utils/SafeCast.test.js

@@ -46,7 +46,6 @@ contract('SafeCast', async (accounts) => {
   describe('toUint256', () => {
     const maxInt256 = new BN('2').pow(new BN(255)).subn(1);
     const minInt256 = new BN('2').pow(new BN(255)).neg();
-    const maxUint256 = new BN('2').pow(new BN(256)).subn(1);
 
     it('casts 0', async function () {
       expect(await this.safeCast.toUint256(0)).to.be.bignumber.equal('0');
@@ -73,13 +72,6 @@ contract('SafeCast', async (accounts) => {
         'SafeCast: value must be positive'
       );
     });
-
-    it(`reverts when casting UINT256_MAX (${maxUint256})`, async function () {
-      await expectRevert(
-        this.safeCast.toUint256(maxUint256),
-        'SafeCast: value must be positive'
-      );
-    });
   });
 
   function testToInt (bits) {