Review some NAD biosynthetic process terms

[pgaudet]

Annotation review template:

https://docs.google.com/spreadsheets/d/13oNsCNrIDGH26TAKCvpDW2QJXT_0vsR0g4qMKygR_b4

• Consider obsoleting 'GO:0034627 de novo' NAD biosynthetic process (1 direct EXP) as an unnecessary grouping term
  (Rossana: Probably this comes from the literature where de novo' NAD synthesis is used to group the Asp and Trp.)
• Consider obsoleting 'GO:0034356 NAD biosynthesis via nicotinamide riboside salvage pathway' (7 direct EXP), since it's a single child of its parent term (we don't have separate terms for the other specific salvage pathways)
• Consider obsoleting 'GO:1905012 regulation of 'de novo' NAD biosynthetic process from L-tryptophan' and it's two children (only 2 TAS annotations to the parent, none to the children), and other terms in this branch don't have regulation terms)