fix(tests): remove obsolete dodal data_session fixture

[ZohebShaikh]

dodal 3.0.2 removed dodal.plan_stubs.data_session (DiamondLightSource/dodal#2201). The path_provider fixture in tests/unit_tests/worker/test_task_worker.py patched get_path_provider in that module, so with 3.0.2 test_worker_and_data_events_produce_in_order errors at setup:

AttributeError: module 'dodal.plan_stubs' has no attribute 'data_session'

Nothing uses that module any more, so this removes the fixture and raises the dls-dodal floor (dev group and demo extra) from >=1.69.0 to >=3.0.2, so the tests never run against a dodal that still has the module. The lock moves to dodal 3.0.2 (ophyd-async 0.21.2 → 0.21.3 comes with it).

just unit: 1035 passed, 1 skipped.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.34%. Comparing base (8160397) to head (9699b20).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1692   +/-   ##
=======================================
  Coverage   96.34%   96.34%           
=======================================
  Files          46       46           
  Lines        3665     3665           
=======================================
  Hits         3531     3531           
  Misses        134      134           

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