[Data] test_operator_fusion.py is broken - not tested in CI

[bveeramani]

Description

The test file python/ray/data/tests/test_operator_fusion.py is currently broken because it was not being run in CI. This test was inadvertently excluded from CI runs, allowing it to become broken over time.

Action Items

• Investigate why this test is broken
• Fix the failing tests in test_operator_fusion.py
• Ensure this test is included in CI runs going forward
• Update semgrep.yml to remove this test from the exclusion list once fixed

Context

This test file was discovered to be excluded from CI testing, which allowed it to break without detection.

Related PR: #57617