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.

approved this merge request

approved this merge request

added ROQ label

changed milestone to %1.1.3

merged

mentioned in commit e9d72733