Release 5.2.4

[jennantilla]

🔧 Native SDK Dependency Updates Only

Update Android SDK from 5.1.17 to 5.1.20 release notes

🐛 Bug Fixes

• IAM with dynamic trigger showing forever (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2137)
• Allow preventDefault to be fired up to two times (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2138)
• Recover null onesignal ID crashes for Operations (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2157) *Prevent retrying IAM display if 410 is received from backend (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2158)

✨ Improvements

• Optimized the initialization process by moving some service initialization to a background thread (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2151)
• Add option to default to HMS over FCM (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2163)
• Remove fallback code for FCM pre-21.0.0 (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2148)
• Clean up Android Support Library references, drop dependency on androidx.legacy, & Android 4.4 and older code (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2147)

Update iOS SDK from 5.2.2 to 5.2.3 release notes

🐛 Bug Fixes

• The user executor needs to uncache first which fixes some cached requests being dropped for past users (https://github.com/OneSignal/OneSignal-iOS-SDK/pull/1465)

✨ Improvements

• Omit misleading fatal-level log for cross-platform SDKs (https://github.com/OneSignal/OneSignal-iOS-SDK/pull/1468)

🛠️ Maintenance

• [For our server] Use only OneSignal ID for requests (https://github.com/OneSignal/OneSignal-iOS-SDK/pull/1464)

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