A couple of minor fixes in NativeToJsBridge

[mganandraj]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Description of changes

These changes will windows builds with systrace turned on. It contains two changes,

1. The change in NativeToJsBridge.cpp removes a statement that we added over the FB's change last year. In other words, it is removing an existing difference.
2. The change in NativeToJsBridge.h fixes a non-standard c++ statement. I've raised a PR in FB repo too : fixing ATOMIC_VAR_INIT call facebook/react-native#26238

Focus areas to test

Build validation should suffice.

Microsoft Reviewers: Open in CodeFlow

[tudorms]

[pull-bot]

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