Atomics: update Atomics.sub to match latest proposed spec change

tc39/ecma262#1908 (comment)

Author: rwaldron

test/built-ins/Atomics/sub/non-shared-bufferdata.js

@@ -14,6 +14,6 @@ testWithAtomicsFriendlyTypedArrayConstructors(TA => {
   );
 
   assert.sameValue(Atomics.store(view, 0, 1), 1, 'Atomics.store(view, 0, 1) returns 1');
-  assert.sameValue(Atomics.sub(view, 0, 1), 0, 'Atomics.sub(view, 0, 1) returns 0');
+  assert.sameValue(Atomics.sub(view, 0, 1), 1, 'Atomics.sub(view, 0, 1) returns 1');
   assert.sameValue(Atomics.load(view, 0), 0, 'Atomics.load(view, 0) returns 0');
 });