assert: remove unneeded condition

Author: Trott

lib/assert.js

@@ -294,7 +294,8 @@ assert.notStrictEqual = function notStrictEqual(actual, expected, message) {
 };
 
 function expectedException(actual, expected) {
-  if (!actual || !expected) {
+  // actual is guaranteed to be an Error object, but we need to check expected.
+  if (!expected) {
     return false;
   }