Bump OneSignal Android SDK

[shepherd-l]

Description

One Line Summary

Updates included OneSignal Android SDK from 5.1.20 to 5.1.21

Details

Motivation

Apply fixes made in the native OneSignal Android SDK to the Unity wrapper SDK.

Scope

Updated included Android SDK from 5.1.20 to 5.1.21

• Fix ending an already ended session
• Fix permissions returned by onRequestPermissionResult when the list is empty
• Fix keyboard input in HTML in-app messages

Testing

Manual testing

Tested OneSignal initialization, app build with Unity 2022.3.10f1 of the OneSignal example app on a emulated Pixel 4 with Android 12.

Affected code checklist

• [ ] Notifications
  • [ ] Display
  • [ ] Open
  • [ ] Push Processing
  • [ ] Confirm Deliveries
• [ ] Outcomes
• [ ] Sessions
• [ ] In-App Messaging
• [ ] REST API requests
• [ ] Public API changes

Checklist

Overview

• [x] I have filled out all REQUIRED sections above
• [x] PR does one thing
  • If it is hard to explain how any codes changes are related to each other then it most likely needs to be more than one PR
• [x] Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• [x] I have included test coverage for these changes, or explained why they are not needed
• [x] All automated tests pass, or I explained why that is not possible
• [x] I have personally tested this on my device, or explained why that is not possible

Final pass

• [x] Code is as readable as possible.
  • Simplify with less code, followed by splitting up code into well named functions and variables, followed by adding comments to the code.
• [x] I have reviewed this PR myself, ensuring it meets each checklist item
  • WIP (Work In Progress) is ok, but explain what is still in progress and what you would like feedback on. Start the PR title with "WIP" to indicate this.

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