remove createReactClass from TimerExample.js (#21623)
remove createReactClass from TimerExample.js (#21623)

Summary:
Relates to #21581
Removed `createdReactClass` from `TimerExample.js`.
Pull Request resolved: https://github.com/facebook/react-native/pull/21623

Reviewed By: hramos

Differential Revision: D10341474

Pulled By: RSNara

fbshipit-source-id: b4bf6e07fcf0355c89709809fe9a69e447b44e2f

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