Remove var in Libraries/emitter/* (#22087)
Remove var in Libraries/emitter/* (#22087)

Summary:
Replaces the keywords var with const in Libraries/emitter/EventValidator.js

If this PR fixes an issue, type "Fixes #issueNumber" to automatically close the issue when the PR is merged.

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

[GENERAL] [ENHANCEMENT] [Libraries/emitter] - remove `var`
Pull Request resolved: https://github.com/facebook/react-native/pull/22087

Differential Revision: D12918444

Pulled By: TheSavior

fbshipit-source-id: 630ccb283fd6c3118a22124a656038eac4a88599

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