CacheSerializableTransactionsTest#testGetRemoveTxNearCache2 (and 1) is flaky

https://ci.ignite.apache.org/project.html?projectId=IgniteTests24Java8&testNameId=4876515758596068461&tab=testDetails&branch_IgniteTests24Java8=%3Cdefault%3E

Problem occurs when two optimistic&serializable transactions are being executed from the same client with near cache, when one of transaction removes key and another updates.
In this scenario near node can be removed from "readers" list if "remove" transaction was completed before "update" transaction.