dillon1000/react

Fix externalization of 'lowPriorityWarning' in fb builds (#9790)

**what is the change?:**
 - Add two more special cases for 'lowPriorityWarning' in 'modules.js',
   treating it the same as 'ReactCurrentOwner'.

**why make this change?:**
Without this, the build was including 'lowPriorityWarning' seemingly both as an external module and as part of the bundle.

**test plan:**
Ran `yarn build` and inspected the `React-dev` build. `lowPriorityWarning` did not get bundled in this time.

**issue:**
None yet - @gaearon flagged this for me directly.