Update dependency firebase/firebase-ios-sdk to from: "10.15.0"

[renovate[bot]]

This PR contains the following updates:

Package	Update	Change
firebase/firebase-ios-sdk	minor	from: "10.14.0" -> from: "10.15.0"

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Release Notes

firebase/firebase-ios-sdk (firebase/firebase-ios-sdk)

### [`v10.15.0`](https://togithub.com/firebase/firebase-ios-sdk/releases/tag/10.15.0): Firebase Apple 10.15.0 [Compare Source](https://togithub.com/firebase/firebase-ios-sdk/compare/10.14.0...10.15.0) The Firebase Apple SDK (10.15.0) is now available. For more details, see the [Firebase Apple SDK release notes.](https://firebase.google.com/support/release-notes/ios#10.15.0) To install this SDK, see [Add Firebase to your project.](https://firebase.google.com/docs/ios/setup)

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