Upgrade dscheck dependency to 0.2.0

[polytypic]

It seems some tests with dscheck 0.1.0 occasionally fail unexpectedly on CI.

Here is a failure on spsc_queue_dscheck test where only the first test runs and then something goes wrong as can be inferred by the output from the test ending:

File "test/spsc_queue/dune", line 5, characters 7-25:
5 |  (name spsc_queue_dscheck)
           ^^^^^^^^^^^^^^^^^^
(cd _build/default/test/spsc_queue && ./spsc_queue_dscheck.exe)
Testing `Spsc_queue_dscheck'.
This run has ID `04E668A0'.

  [OK]          basic                 0   simple-test.
(cd _build/default/test/michael_scott_queue && ./michael_scott_queue_dscheck.exe)

Here is log output from another failure

2023-11-16 14:18.57: >>> [FAIL]        basic          0   2-mem. (score = 30)
2023-11-16 14:18.57: >>> [FAIL]        basic          1   2-add-same. (score = 30)
2023-11-16 14:18.57: >>> [FAIL]        basic          2   2-add. (score = 30)
2023-11-16 14:18.57: >>> [FAIL]        basic          3   2-remove-same. (score = 30)
2023-11-16 14:18.57: >>> [FAIL]        basic          4   2-remove. (score = 30)
2023-11-16 14:18.57: >>> [FAIL]        basic          0   2-mem.                                      │ (score = 30)
2023-11-16 14:18.57: >>> [exception] File "src/tracedAtomic.ml", line 193, characters 12-18: Assertion failed (score = 35)
2023-11-16 14:18.57: >>> [FAIL]        basic          1   2-add-same.                                 │ (score = 30)
2023-11-16 14:18.57: >>> [exception] Stdlib.Effect.Unhandled(Dscheck.TracedAtomic.Make(0)) (score = 35)
2023-11-16 14:18.57: >>> [FAIL]        basic          2   2-add.                                      │ (score = 30)
2023-11-16 14:18.57: >>> [exception] Stdlib.Effect.Unhandled(Dscheck.TracedAtomic.Make(0)) (score = 35)
2023-11-16 14:18.57: >>> [FAIL]        basic          3   2-remove-same.                              │ (score = 30)
2023-11-16 14:18.57: >>> [exception] Stdlib.Effect.Unhandled(Dscheck.TracedAtomic.Make(0)) (score = 35)
2023-11-16 14:18.57: >>> [FAIL]        basic          4   2-remove.                                   │ (score = 30)
2023-11-16 14:18.57: >>> [exception] Stdlib.Effect.Unhandled(Dscheck.TracedAtomic.Make(0)) (score = 35)
2023-11-16 14:18.57: Exception: File "src/tracedAtomic.ml", line 193, characters 12-18: Assertion failed

which seems to point to a bug within dscheck (an unhandled effect?).