Remove TimerMixin on ReactContentSizeUpdateTest (#21502)
Remove TimerMixin on ReactContentSizeUpdateTest (#21502)

Summary:
Related to #21485.
Removed `TimerMixin` from `ReactContentSizeUpdateTest`.
Pull Request resolved: https://github.com/facebook/react-native/pull/21502

Reviewed By: TheSavior

Differential Revision: D10218548

Pulled By: RSNara

fbshipit-source-id: 9a0642e14f8548d8dc9683f0f70353416ed04ae0

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