Fix unittest related to the dir hash in MacOS

[tatiana]

Feedback from https://github.com/astronomer/astronomer-cosmos/pull/1322/files#r1842807048

Just fyi: I'm on macOS (so Darwin) and I had to change 25beeb54cc4eeabe6198248e286a1cfe in line 1582 to 6f63493009733a7be34364a6ea3ffd3c (= the value in line 1584) in my local repo in order to get the unit test to pass.
astronomer-cosmos/tests/dbt/test_graph.py

Lines 1581 to 1584 in 8ec46d2

	 if sys.platform == "darwin": 
	     assert hash_dir == "25beeb54cc4eeabe6198248e286a1cfe" 
	 else: 
	     assert hash_dir == "6f63493009733a7be34364a6ea3ffd3c" 

[tatiana]

As a reference, on my MacBook I got the following error when running hatch run tests.py3.10-2.7:test-cov:

FAILED tests/dbt/test_graph.py::test_save_dbt_ls_cache - AssertionError: assert '400457eb6664cd604a1af9e06c07a620' == '25beeb54cc4eeabe6198248e286a1cfe'
  
  - 25beeb54cc4eeabe6198248e286a1cfe
  + 400457eb6664cd604a1af9e06c07a620

The version of python and other local configuration may affect the value of this test locally. The important part is to guarantee that for a given environment, if it is run twice, it will return the same value. We can probably refactor the test so it is more deterministic when devs run it locally.