**breaking:** remove YGNodeGetInstanceCount

Summary:
@public

`YGNodeGetInstanceCount` was only ever meant for tests, and caused data races in multi-threaded environments.

It was completely replaced with event-based counting for tests.

Here we remove public API around the counter, and the counter itself.

Reviewed By: SidharthGuglani

Differential Revision: D15174857

fbshipit-source-id: 228e85da565bac9e8485121e956a2e41910b11c8

javascript/sources/global.cc

@@ -1,13 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- *
- * This source code is licensed under the MIT license found in the LICENSE
- * file in the root directory of this source tree.
- */
-#include <yoga/Yoga.h>
-
-#include "./global.hh"
-
-unsigned getInstanceCount(void) {
-  return YGNodeGetInstanceCount();
-}