Update ET to use ET-D noise curve

The ET interferometer object defaults to using the ET-B noise curve. However, the ET Collaboration requests the use of the ET-D noise curve for simulations, and ET-D has been the norm for a long time. The official reference for this noise curve is ET-0000A-18 in the ET document control system, but it is the same as the ET-D curve currently in the repository. This MR changes the default to use the ET-D noise curve.

added <10 lines Detector labels

assigned to @gregory.ashton

changed the description

approved this merge request

changed milestone to %1.4.2

approved this merge request

merged

mentioned in commit e239f78a

Thanks @john-veitch!