[Security solution][Detection Engine] removes skipped "alerts index does not exist" FTR test

[vitaliidm]

Summary

• addresses [Detection Engine][FTR] Unskip skipped tests in x-pack/test/security_solution_api_integration/test_suites/detections_response/detection_engine/alerts/basic_license_essentials_tier/ess_specific_index_logic/create_index.ts #179208 by removing skipped test

I tracked skipped test to this PR: #115290

Test was added already skipped https://github.com/elastic/kibana/pull/115290/files#diff-16cebcbaef99c1aab50640a5bee66351bcbfd7575361d97eee4d2ca6753f5a27R38-R41

In the tested route itself, when index does not exist, it returns 200: https://github.com/elastic/kibana/pull/115290/files#diff-a4e27aaa05560a7737e153e53fe4bdaf839056180347c338e8d0842ab39f1240R79-R84

So, test from the very beginning was not testing valid use case.

After talking to PR author @marshallmain , we agreed to remove that test

[vitaliidm]

/ci

[kibana-ci]

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cc @vitaliidm

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