After submitting Unity-iOS builds to the App Store Connect, Apple is showing a Warning for using UIWebView in Unity Ads:

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Dear Developer,
We identified one or more issues with a recent delivery for your app, "XXXXX". Your delivery was successful, but you may wish to correct the following issues in your next delivery:
ITMS-90809: Deprecated API Usage - Apple will stop accepting submissions of apps that use UIWebView APIs . See https://developer.apple.com/documentation/uikit/uiwebview for more information.
After you’ve corrected the issues, you can use Xcode or Application Loader to upload a new binary to App Store Connect.
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This case doesn't need a reproduction project, the problem is that we're creating instances of UIWebView in Unity Ads, but the UIWebView will be no longer supported by Apple and will be a cause for apps rejection in the App Store Connect.

Notes:
- This case is different from case 1180664 because this is about the UIWebView implementations on Ads only
- More info is in Comments section

Reproduced on Unity 2017.4.32f1, 2018.4.9f1, 2019.2.6f1, 2019.3.0b4 and 2020.1.0a5