test: fix broken unit tests

[jwilliams-ocient]

SUMMARY

Fixes the failing unit tests blocking merge. A test case was removed because it tests functionality that the OCient engine does not implement.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

========== 10 passed, 512 warnings in 8.60s ==========

TESTING INSTRUCTIONS

pytest --durations-min=0.5 --cov-report= --cov=superset  --cache-clear tests/unit_tests/db_engine_specs/test_ocient.py

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API