Tapered GR regression WUS gridded seismicity sources

Tapered GR sources (10% wt; mMax=8) in the WUS gridded source models have incorrect mMax=7.5.

changed milestone to %Beta release of CONUS NSHM

added ERF label

Resolved in !81 (merged)
See https://code.usgs.gov/ghsc/nshmp/nshms/nshm-conus/-/tags/5.3.0

closed