Update fflib_SObjectSelectorTest.cls

Fixed test failures:

System.AssertException: Assertion Failed: Expected: Permission to access an Account dennied., Actual: Permission to access an Account denied.
Class.fflib_SObjectSelectorTest.testAssertIsAccessible: line 132, column 1

System.AssertException: Assertion Failed: Expected: Name,AccountNumber,Id,AnnualRevenue, Actual: AccountNumber,AnnualRevenue,Id,Name
Class.fflib_SObjectSelectorTest.testDefaultConfig: line 177, column 1

System.AssertException: Assertion Failed: Expected: myprefix.Name,myprefix.Id,myprefix.AccountNumber,myprefix.AnnualRevenue, Actual: myprefix.AccountNumber,myprefix.AnnualRevenue,myprefix.Id,myprefix.Name
Class.fflib_SObjectSelectorTest.testGetFieldListString: line 43, column 1