Declare pytest-timeout as a test dependency

[nathanjmcdougall]

It's being used here, for example:

pyemu/autotest/utils_tests.py

Lines 826 to 827 in 5dd3c78

	@pytest.mark.timeout(method='thread', timeout=90)
	def geostat_prior_builder_test(tmp_path):

At the moment, this isn't declared as a dependency so when trying to collect the pytest tests, a warning is emitted:

>> pytest autotest --collect-only 

...

autotest\utils_tests.py:826
  C:\Users\namc\Repositories\pyemu\autotest\utils_tests.py:826: PytestUnknownMarkWarning: Unknown pytest.mark.timeout - is this a typo?  You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/stable/how-to/mark.html

[mwtoews]

Same fix in #643

[briochh]

now covered off by #668