Fabric: Fixed incorrect systrace marker in UIManagerBinding::dispatchEvent
Fabric: Fixed incorrect systrace marker in UIManagerBinding::dispatchEvent

Summary: `SystraceSection` relies on RAII, so previously it measured only `if (eventTarget) {`'s body.

Reviewed By: mdvacca

Differential Revision: D13123047

fbshipit-source-id: 463fba783763f694b51325f98314d36b7da2f887

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