chore(Podfile): fixed URL to New Arch info (#37535)

Summary:
I was following the upgrade helper from [0.71.7 -> 0.72.0-rc.3](https://react-native-community.github.io/upgrade-helper/?from=0.71.7&to=0.72.0-rc.3) and came across a comment with a URL in the Podfile changes. That comment lead to a 404, so this updates that to the correct URL.

Confirmed this was an issue on the [Roadmap to 0.72.0](reactwg/react-native-releases#54 (comment))

## Changelog:

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[IOS] [CHANGED] - Message

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[IOS] [CHANGED] - fixed URL to New Arch info

Pull Request resolved: #37535

Test Plan: Only updated a comment, no code changes

Reviewed By: cortinico

Differential Revision: D46145428

Pulled By: cipolleschi

fbshipit-source-id: 600274222725567e1cbae041a3dac9561da15aff

packages/react-native/template/ios/Podfile

@@ -51,7 +51,7 @@ target 'HelloWorld' do
   end
 
   post_install do |installer|
-    # https://github.com/facebook/react-native/blob/main/scripts/react_native_pods.rb#L197-L202
+    # https://github.com/facebook/react-native/blob/main/packages/react-native/scripts/react_native_pods.rb#L197-L202
     react_native_post_install(
       installer,
       config[:reactNativePath],