[builtins] Fix typo in PromiseResolve fast-path.

The PromiseResolve builtin was missing it's fast-path for when we can
skip the "constructor" lookup due to a typo.

Bug: v8:7253
Change-Id: Icca033af5d4f7fe8b43ebf49c9315b4c80d52cbc
Reviewed-on: https://chromium-review.googlesource.com/955483Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51807}

src/builtins/builtins-promise-gen.cc

@@ -1171,7 +1171,7 @@ TF_BUILTIN(PromiseResolve, PromiseBuiltinsAssembler) {
   // intact, as that guards the lookup path for "constructor" on
   // JSPromise instances which have the (initial) Promise.prototype.
   Node* const promise_prototype =
-      LoadContextElement(native_context, Context::PROMISE_FUNCTION_INDEX);
+      LoadContextElement(native_context, Context::PROMISE_PROTOTYPE_INDEX);
   GotoIfNot(WordEqual(LoadMapPrototype(value_map), promise_prototype),
             &if_slow_constructor);
   GotoIf(IsSpeciesProtectorCellInvalid(), &if_slow_constructor);