remove createReactClass and TImerMixin from TimerTest.js (#21748)
remove createReactClass and TImerMixin from TimerTest.js (#21748)

Summary:
Related to https://github.com/facebook/react-native/issues/21485#issuecomment-428742440
Remove createReactClass and TimerMixin from IntegrationTests/TimersTest.js
Pull Request resolved: https://github.com/facebook/react-native/pull/21748

Reviewed By: TheSavior

Differential Revision: D10366418

Pulled By: RSNara

fbshipit-source-id: f7e9a1b62a17cd23374997f99dbfe239172b614f

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