Summary: Update `react-devtools-core` and `react-devtools` dependencies for RN, VSCode, Flipper, etc. `js1 upgrade react-devtools -v 4.20.0` # Changelog: [General][Changed] - Upgraded react-devtools-core dependency to 4.20.0 Reviewed By: bvaughn Differential Revision: D31694359 fbshipit-source-id: d05d75e9473878828617c5cd0db8d6008b6abd4d