Removing `np.str_` injection parameters
The purpose of this MR is to remove np.str_
injection parameters when loading in a bilby
result file. This prevents the following error from being raised:
Failed to read in ...merge_result.hdf5 with the <bound method Read.load_file of <class 'pesummary.gw.file.formats.bilby.Bilby'>> class because must be real number, not numpy.str_