Add HoftOnline as a preferred frametype
Created by: dethodav
This PR adds HoftOnline as one of the HIGH_PRIORITY_TYPE frametypes in gwpy.io.datafind.
The "standard" Virgo strain frametype has changed in O4 from V1Online to HoftOnline, but it not yet updated in gwpy.
@jacobgolomb noted that this issue prevents bilby_pipe from automatically identifying the correct Virgo frametype to use in O4.