Fix ParseClientConfigurationTests.testExtensionDataSharing

[cbaker6]

This test isn't working in Xcode 12 and it seems to be something with FileManager, entitlements, or the swizzler. Noted in #1581. Some notes from the discussion

I see two possible issues the test brings up. Either users are able to do something in Xcode 12 (meaning iOS 14) that they weren't able to do in previous versions or there's an access change in PFFileManager that needs to be fixed. In either case, people are already using this SDK in Xcode 12 and this specific PR doesn't need the fix or stop people from using Xcode 12. Running the tests in Xcode 11 would just give us a green check mark, but the issue will still be present.

Shot in the dark, but this might be as simple as a group entitlement issue, https://developer.apple.com/documentation/bundleresources/entitlements/com_apple_security_application-groups