`BasicsTests.Integration_Cassandra_Timestamps` is flaky

[wprzytula]

The test checks that the timestamps of two subsequent writes differ at most by some predefined value. The tolerance threshold was originally set to 100ms, but in 2022 increased by @Gor027 to 150ms to reduce flakiness on GH Actions machines.

We can fight the flakiness by increasing the threshold more aggressively, or remove the check altogether. To me, this particular check seems not to bring much value to the test.