Nullsafe fabric/events classes

[tdn120]

Summary: Updating null annotations to match convention.

Changelog: [Internal]

Differential Revision: D56895070

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D56895070

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	19,495,291	+4
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	22,867,616	-6
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: 06eea61c19cd730cf0c14a436f042d30791c3f4a Branch: main

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D56895070

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D56895070

[facebook-github-bot]

This pull request has been merged in facebook/react-native@3f59d53281ac0dd1e019de4769a9c44629ba656f.

[github-actions[bot]]

This pull request was successfully merged by Thomas Nardone in 3f59d53281ac0dd1e019de4769a9c44629ba656f.

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