merge some pairs of larval gustatory neurons

[Clare72]

There is nothing to discriminate the A1 and A2 neurons of the larval dorsal organ from each other in the original publication (Kwon et al., 2011 - FBrf0216529), or that I can find in any later publications. They have the same soma and dendrite locations and express the same receptors, so may actually be the same cell type (just 2/side unlike most other larval GRNs). These should be merged with the parent term.
There is no associated curation in FlyBase.

[Clare72]

Similarly VP1/2 and VP4/5 are also indistinguishable based on the original reference (Choi et al., 2016 - FBrf0233050) and these pairs should probably be merged. Curation within each pair is identical.