completeTransactions() is not called at app starts when there are unfinished transactions in iOS 14

## Bug Report
completeTransactions() is not called at app starts when there are unfinished transactions in iOS 14

**To Reproduce**
Steps to reproduce the behavior:
1. call purchaseProduct() with atomically is false and purchase succeed
2. stop app without finishing this transaction when completion closure is called.
3. run app again
4. completeTransactions() is not called when app starts

**Expected behavior**
I expected for completeTransactions() be called at app starts. and it did be called when I run the same code and do the same steps in iOS 13.4.1

## Platform Information
- OS: iOS 14.4
- Purchase Type: consumable
- Environment: sandbox
- SwiftyStoreKit version: 0.16.1