remove createrReactClass from SizeFlexibilityUpdateTest (#21715)
remove createrReactClass from SizeFlexibilityUpdateTest (#21715)

Summary:
Related to #21581 .
Removed createReactClass from the IntegrationTests/SizeFlexibilityUpdateTest.js

 - [x] npm run prettier
 - [x] npm run flow-check-ios
 - [x] npm run flow-check-android

[GENERAL] [ENHANCEMENT] [IntegrationTests/SizeFlexibilityUpdateTest.js] - remove createReactClass dependency
Pull Request resolved: https://github.com/facebook/react-native/pull/21715

Reviewed By: TheSavior

Differential Revision: D10341543

Pulled By: RSNara

fbshipit-source-id: 748f9a0176b6cd865d956df774f6dec1ead21562

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