fix typo in README.md (#20993)
fix typo in README.md (#20993)

Summary:
The original facebook is misspelled.
pass all current ci.
none
 [GENERAL] [INTERNAL] [MISC] - fix typo in README.md
Pull Request resolved: https://github.com/facebook/react-native/pull/20993

Differential Revision: D9671977

Pulled By: hramos

fbshipit-source-id: 2c279cb681696460801e11012b4a456d5375ce24

exponent/react-native,hoangpham95/react-native,javache/react-native,pandiaraj44/react-native,pandiaraj44/react-native,myntra/react-native,pandiaraj44/react-native,arthuralee/react-native,hammerandchisel/react-native,facebook/react-native,exponent/react-native,arthuralee/react-native,myntra/react-native,pandiaraj44/react-native,exponent/react-native,myntra/react-native,exponentjs/react-native,hoangpham95/react-native,janicduplessis/react-native,arthuralee/react-native,javache/react-native,facebook/react-native,exponentjs/react-native,janicduplessis/react-native,myntra/react-native,myntra/react-native,hammerandchisel/react-native,myntra/react-native,hoangpham95/react-native,janicduplessis/react-native,myntra/react-native,hammerandchisel/react-native,pandiaraj44/react-native,exponent/react-native,hoangpham95/react-native,exponentjs/react-native,hoangpham95/react-native,hoangpham95/react-native,hoangpham95/react-native,pandiaraj44/react-native,janicduplessis/react-native,javache/react-native,hammerandchisel/react-native,exponentjs/react-native,exponent/react-native,janicduplessis/react-native,myntra/react-native,janicduplessis/react-native,hammerandchisel/react-native,facebook/react-native,janicduplessis/react-native,facebook/react-native,javache/react-native,exponent/react-native,exponentjs/react-native,pandiaraj44/react-native,exponent/react-native,exponentjs/react-native,janicduplessis/react-native,facebook/react-native,hammerandchisel/react-native,arthuralee/react-native,javache/react-native,facebook/react-native,javache/react-native,javache/react-native,hammerandchisel/react-native,javache/react-native,exponentjs/react-native,exponentjs/react-native,javache/react-native,exponent/react-native,facebook/react-native,hoangpham95/react-native,hammerandchisel/react-native,myntra/react-native,pandiaraj44/react-native,arthuralee/react-native,facebook/react-native,facebook/react-native