Add " atom" to labels of subclasses of CHEBI_33250 ("atom")

[jmkeil]

I think the labels of the following entities should all end with " atom" to be consistent in naming:

• http://purl.obolibrary.org/obo/CHEBI_5631 (heavy metal)
• http://purl.obolibrary.org/obo/CHEBI_24473 (halogen)
• http://purl.obolibrary.org/obo/CHEBI_27998 (tungsten)
• http://purl.obolibrary.org/obo/CHEBI_30440 (thallium)
• http://purl.obolibrary.org/obo/CHEBI_33300 (pnictogen)
• http://purl.obolibrary.org/obo/CHEBI_33303 (chalcogen)
• http://purl.obolibrary.org/obo/CHEBI_33363 (palladium)
• http://purl.obolibrary.org/obo/CHEBI_33364 (platinum)
• http://purl.obolibrary.org/obo/CHEBI_33367 (darmstadtium)
• http://purl.obolibrary.org/obo/CHEBI_33369 (cerium)
• http://purl.obolibrary.org/obo/CHEBI_33371 (technetium-99)
• http://purl.obolibrary.org/obo/CHEBI_33379 (erbium)
• http://purl.obolibrary.org/obo/CHEBI_33381 (ytterbium)
• http://purl.obolibrary.org/obo/CHEBI_33385 (thorium)
• http://purl.obolibrary.org/obo/CHEBI_33394 (fermium)
• http://purl.obolibrary.org/obo/CHEBI_33396 (nobelium)
• http://purl.obolibrary.org/obo/CHEBI_37802 (thallium-203)
• http://purl.obolibrary.org/obo/CHEBI_37803 (thallium-205)
• http://purl.obolibrary.org/obo/CHEBI_37804 (thallium-201)
• http://purl.obolibrary.org/obo/CHEBI_37805 (thallium-199)
• http://purl.obolibrary.org/obo/CHEBI_50076 (chromium-51)
• http://purl.obolibrary.org/obo/CHEBI_52462 (tungsten-183)
• http://purl.obolibrary.org/obo/CHEBI_52619 (cadmium-111)
• http://purl.obolibrary.org/obo/CHEBI_52620 (cadmium-113)
• http://purl.obolibrary.org/obo/CHEBI_52633 (molybdenum-95)
• http://purl.obolibrary.org/obo/CHEBI_88184 (metal allergen)