FutureWarning: pandas read_csv `delim_whitespace` argument will be depracated

[jlmaurer]

The following warning is raised when running the raiderDownloadGNSS.py script:

FutureWarning: The 'delim_whitespace' keyword in pd.read_csv is deprecated and will be removed in a future version. Use ``sep='\s+'`` instead

Should be a simple fix to update the syntax as we don't use delim_whitespace in many places.