Fix intermittently failing schema evolution UT

[ypatia]

Nightlies have been failing often on MacOS and ubuntu machines. I have reproduced locally on my laptop as well. This is fixing the flaky behavior by making sure we remove and add an attribute to an array at the same timestamp, causing non deterministic schema evolution result.

This also removes a wrong assert that fails when building in debug mode.

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TYPE: NO_HISTORY DESC: Fix intermittently failing schema evolution UT