Census: more same-registry spellings remain unfolded after #244

[realmarcin]

From the round-1 review of #244 (#84).

A scan of every census record at the #120 pins finds more spellings of registries the census counts, written the same way as the ones #244 folds, still uncounted:

spelling	folds into	Mech	occurrences
SwissProt, swissprot, Swissprot, UNIPROT	UniProt	ProteinTraitsMech	17
TAXON	NCBITaxon	ProteinTraitsMech	5
PDBe, pdbe	PDB	ProteinTraitsMech	10
interpro	InterPro	ProteinTraitsMech	2
KEGG_PATHWAY, kegg.module	KEGG	ProteinTraitsMech	5
kegg.glycan	KEGG	AntibioticMech	1
MeSH	MESH	ProteinTraitsMech, MediaIngredientMech	5
PubChem_Compound	PubChem	ProteinTraitsMech	1

Five of these fold into heatmap columns (UniProt, NCBITaxon, PDB, InterPro, KEGG). #244's title, the README and the code comment claim every spelling is folded.

Fix: fold these in the census and, for the columns, in build_subsets. Scope the claim to the spellings measured at the pins.