Remove legacy tests

[taldcroft]

Description

These "tests" have not been run in years. They fall in a few categories:

• Do not actually test anything.
• Depend on non-existent files.
• Redundant with other unit tests.

In all cases they are not written as proper tests and end up failing in pytest test collection.

Interface impacts

Testing

Unit tests

• Mac

Note that a plain pytest now works as expected.

(ska3-flight-2025.0rc2) ➜  xija git:(remove-legacy-tests) git rev-parse --short HEAD                    
1a3951a
(ska3-flight-2025.0rc2) ➜  xija git:(remove-legacy-tests) pytest
===================================================== test session starts ======================================================
platform darwin -- Python 3.12.8, pytest-8.3.4, pluggy-1.5.0
rootdir: /Volumes/git
configfile: pytest.ini
plugins: doctestplus-1.3.0, anyio-4.7.0, timeout-2.3.1
collected 44 items                                                                                                             

xija/tests/test_get_model_spec.py .......                                                                                [ 15%]
xija/tests/test_models.py .....................................                                                          [100%]

===================================================== 44 passed in 35.03s ======================================================

Independent check of unit tests by [REVIEWER NAME]

• [PLATFORM]:

Functional tests

No functional testing.