gwastro/pycbc: v2.1.2 release of PyCBC

This is the v2.1.2 release of PyCBC. The 2.1.x release line will be reserved for production PyCBC Live analyses throughout the first part of O4, and possibly for the entire run, depending on development activities over the next year. It should therefore only contain backports from the master branch related to PyCBC Live. 2.1.2 fixes a few bugs and adds a few convenience features, namely: the ability to apply GraceDB labels to SNR-optimized events, the ability to record when significance (FAR and/or followup p-value) is saturated, and options to control the mass-gap parameters from the command line. A Docker container for this release is available from the pycbc/pycbc-el8 repository on Docker Hub and can be downloaded using the command: docker pull pycbc/pycbc-el8:v2.1.2 On a machine with CVMFS installed, a pre-built virtual environment is available for Red Hat 8 compatible operating systems by running the command: source /cvmfs/oasis.opensciencegrid.org/ligo/sw/pycbc/x86_64_rhel_8/virtualenv/pycbc-v2.1.2/bin/activate A singularity container is available at /cvmfs/singularity.opensciencegrid.org/pycbc/pycbc-el8:v2.1.2 which can be started with the command: singularity shell --home ${HOME}:/srv --pwd /srv --bind /cvmfs --contain --ipc --pid /cvmfs/singularity.opensciencegrid.org/pycbc/pycbc-el8:v2.1.