Fix Version/s: None
The following hack was put into fgcmcal some time ago to force the filters to be loaded when building a lookup table. This is no longer necessary because of the change to filterLabel, and Nate Lust points out that usage of butlerQC.registry is dangerous in the case of execution butlers. This appears to be the only use of butlerQC.registry in the stack, and this should not have been publicly exposed in the first place.
PR is here: https://github.com/lsst/fgcmcal/pull/67
Jenkins is here: https://ci.lsst.codes/blue/organizations/jenkins/stack-os-matrix/detail/stack-os-matrix/34830/pipeline