Fix "DeprecationWarning: invalid escape sequence" warnings

(cml_foo) mjw@lags:~/workspace/nwchemcmlutils$ pytest ./nwchemcmlutils/test/NWChemCMLUtilScriptTests.py 
================================================================================= test session starts =================================================================================
platform linux -- Python 3.7.10, pytest-6.2.3, py-1.10.0, pluggy-0.13.1
rootdir: /home/mjw/workspace/nwchemcmlutils
collected 296 items                                                                                                                                                                   

nwchemcmlutils/test/NWChemCMLUtilScriptTests.py ............................................................................................................................... [ 42%]
.........................................................................................................................................................................       [100%]

================================================================================== warnings summary ===================================================================================
nwchemcmlutils/test/nwinfilegentest/ziggy_submit_generator_test.py:210
  /home/mjw/workspace/nwchemcmlutils/nwchemcmlutils/test/nwinfilegentest/ziggy_submit_generator_test.py:210: DeprecationWarning: invalid escape sequence \$
    """

Seems like the solution is here: https://stackoverflow.com/questions/50504500/deprecationwarning-invalid-escape-sequence-what-to-use-instead-of-d