gaussian_format: Verify if `get_charges_form_log` works without IOp(6/50=1)

[jszopi]

This is regarding the parsing of MK and ESP charges from Gaussian .log output files. There was a comment in the old code that the line used to detect the end of the charges section varies between files generated with and without the IOp(6/50=1) override.

def _charge_termination_line(input_type, charge_type):
    """Returns the first 8 characters of the charge section termination line"""
     ...
            # The latter happens when IOp(6/50=1) is requested
            return [' Sum of ', ' Charges']

The comment is incorrect, since the new code uses "Sum of" and passes tests on files generated with the IOp(6/50=1) override. Output files generated without the override are necessary to find out whether the new code works on them. If it does not, the library will have to be adapted or mention in the docs that the override is required.