Firestore emulator problem when 2 transactions in parallel are creating same document

### [REQUIRED] Environment info

**firebase-tools:** 12.9.1

**Platform:** Windows 10

### [REQUIRED] Test case

When executing same transaction completely in parallel (2 executions going in parallel), if both transactions are creating a same document then neither transaction is going to succeed, both transactions fail.

_Error which both transactions receive_: **(StatusCode="Aborted", Detail="Transaction lock timeout.")**

### [REQUIRED] Steps to reproduce

Execute 2 transactions in parallel which are creating the same document in a same collection.

**Transaction configuration:** Only 1 attempt

### [REQUIRED] Expected behavior

At least one transaction to succeed.

### [REQUIRED] Actual behavior

Neither transaction succeed.