Remove invalid test from ArrayBuffer subclassing

Fixes gh-696

As pointed in gh-696, the ArrayBuffer ctor won't throw a RangeError when
invoked without arguments.

Instead of fixing the invalid assertion, this commit removes it as the
coverage for subclassing is already satisfied by the use of slice.

test/language/statements/class/subclass/builtin-objects/ArrayBuffer/regular-subclassing.js

@@ -24,8 +24,3 @@ var sliced = ab.slice(0, 1);
 
 assert(sliced instanceof AB);
 assert(sliced instanceof ArrayBuffer);
-assert.notSameValue(ab, sliced);
-
-assert.throws(RangeError, function() {
-  new AB();
-});