Rename default RN transformer

Differential Revision: D8235001

fbshipit-source-id: 59a4b2f13185dd9be0d33f01589d907d49493a26

jest/preprocessor.js

@@ -34,7 +34,7 @@ const nodeOptions = babelRegisterOnly.config([nodeFiles]);
 babelRegisterOnly([]);
 
 /* $FlowFixMe(site=react_native_oss) */
-const transformer = require('metro/src/transformer.js');
+const transformer = require('metro/src/reactNativeTransformer');
 module.exports = {
   process(src /*: string */, file /*: string */) {
     if (nodeFiles.test(file)) {
@@ -118,7 +118,7 @@ module.exports = {
 
   getCacheKey: createCacheKeyFunction([
     __filename,
-    require.resolve('metro/src/transformer.js'),
+    require.resolve('metro/src/reactNativeTransformer'),
     require.resolve('@babel/core/package.json'),
   ]),
 };