bilby/gw/likelihood.py: Fix a bug in the algorithm to determine time resolution of ROQ

It seems there are 2 bugs in the algorithm to determine the time resolution for ROQ.

1. InterferometerList doesn't have optimal_SNR as an attribute, but it does as an key.
2. min should be replaced by max for conservative estimates.

This merge request is to fix them.

bilby/gw/likelihood.py

@@ -1625,7 +1625,7 @@ class ROQGravitationalWaveTransient(GravitationalWaveTransient):
 
         inj_snr_sq = 0
         for ifo in self.interferometers:
-            inj_snr_sq += min(10, getattr(ifo.meta_data, 'optimal_SNR', 30))**2
+            inj_snr_sq += max(10, ifo.meta_data.get('optimal_SNR', 30))**2
 
         psd = ifo.power_spectral_density_array[ifo.frequency_mask]
         freq = ifo.frequency_array[ifo.frequency_mask]