LibJS: Stub out Atomics.notify

We don't have the facilities to implement this method fully (namely, a
fully realized SharedArrayBuffer). But we can implement enough to
validate the values passed in by the user.

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -387,6 +387,7 @@ namespace JS {
     P(next)                                  \
     P(normalize)                             \
     P(notation)                              \
+    P(notify)                                \
     P(now)                                   \
     P(numberingSystem)                       \
     P(numeric)                               \