import correct babel register (facebook#46987)

Summary:

X-link: facebook/metro#1371

Update `babel/register` to latest version, fixing the bug that were preventing us from updating it previously.

Differential Revision: D64245277

scripts/build/babel-register.js

@@ -30,7 +30,11 @@ function registerForMonorepo() {
     return;
   }
 
-  require('metro-babel-register')([PACKAGES_DIR]);
+  if (process.env.FBSOURCE_ENV === '1') {
+    require('@fb-tools/babel-register');
+  } else {
+    require('metro-babel-register')([PACKAGES_DIR]);
+  }
 
   isRegisteredForMonorepo = true;
 }