Include mandatory NSLocationUsageDescription on macOS

[rschiang]

Starting from macOS Big Sur, location usage description has been enforced on new apps. Apps that fail to include the aforementioned description would cause an outright crash (thus the issue encountered in #655). stderr log shows the following error when Telegram.app attempts to access Location for the first time:

2021-10-12 12:43:06.412 Telegram[42052:1582640] This app has attempted to access privacy-sensitive data without a usage description. The app's Info.plist must contain an “NSLocationUsageDescription” key with a string value explaining to the user how the app uses this data

It is true that the current Info.plist already contains NSLocationWhenInUseUsageDescription, which is the said property key for iOS. However, as documented by Apple, macOS uses a different property key called NSLocationUsageDescription:

If you need location information in a macOS app, use NSLocationUsageDescription instead.

And in NSLocationUsageDescription’s documentation:

This key is required if your macOS app uses APIs that access the user’s location information.

This pull request should fix the issue.

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