Update contracts to support Solidity 0.8.x (#2442)

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

test/utils/Counters.test.js

@@ -43,7 +43,7 @@ contract('Counters', function (accounts) {
 
       it('reverts if the current value is 0', async function () {
         await this.counter.decrement();
-        await expectRevert(this.counter.decrement(), 'SafeMath: subtraction overflow');
+        await expectRevert.unspecified(this.counter.decrement());
       });
     });
     context('after incremented to 3', function () {