Fix broken unit and integration tests

[ohltyler]

Issue #, if available:

Description of changes:

This PR fixes the unit and integration test suites to successfully pass in the GitHub runners.

Specifically:

• Removes unit test snapshots that included timestamp conversion logic, causing it to fail in the GitHub runners that run in UTC time.
• Updates wording on 3 integration tests.

UT successful run: https://github.com/ohltyler/anomaly-detection-kibana-plugin/actions/runs/504899719 IT successful run: https://github.com/ohltyler/anomaly-detection-kibana-plugin/actions/runs/504899716

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