inspiral_range function bugged when SNR!=8

Created by: dethodav

When using the gpwy.astro.inspiral_range() function, there is an issue with the calculated range when snr!=8. The following example demonstrates the problem:

from gwosc.datasets import event_gps
from gwpy.timeseries import TimeSeries
from gwpy.astro import sensemon_range, inspiral_range

gps = event_gps("GW150914")
data = TimeSeries.fetch_open_data('L1', gps-32, gps+32, cache=True)

psd = data.psd(4,2)

snrs = [2,8,16]
fmin = 10
fmax = 100

for s in snrs:
    print('SNR = %d'%s)
    r_sensemon = sensemon_range(psd, fmin=fmin, fmax=fmax, snr=s)
    r_astro = inspiral_range(psd, fmin=fmin, fmax=fmax, snr=s)
    print('sensemon range: %.2f Mpc'%r_sensemon.value)
    print('inspiral range: %.2f Mpc'%r_astro.value)
    print('ratio, sensemon/inspiral: %.2f'%(r_sensemon.value/r_astro.value))
    print()

This returns:

SNR = 2
sensemon range: 175.12 Mpc
inspiral range: 42.60 Mpc
ratio, sensemon/inspiral: 4.11

SNR = 8
sensemon range: 43.78 Mpc
inspiral range: 42.72 Mpc
ratio, sensemon/inspiral: 1.02

SNR = 16
sensemon range: 21.89 Mpc
inspiral range: 36.23 Mpc
ratio, sensemon/inspiral: 0.60

While the sensemon range function returns sensible results, there is (roughly) a , missing factor of 8 / SNR in the inspired range calculation. This is likely due to the sir value not being passed to range_func() here:

https://github.com/gwpy/gwpy/blob/main/gwpy/astro/range.py#L439