chore: rename delaborators to match naming convention (leanprover-community#39822)

Change from delab_foo to delabFoo (as these are Type-valued, not Prop-valued, so should be lowerCamelCase by naming rule 4).

This should not need deprecations, as presumably these delaborators are never called directly. Found by the linter added in leanprover-community#34519.

Author: grunweg

Mathlib/Data/Set/Notation.lean

@@ -46,7 +46,7 @@ If the `Set.Notation` namespace is open, sets of a subtype coerced to the ambien
 represented with `↑`.
 -/
 @[scoped delab app.Set.image]
-meta def delab_set_image_subtype : Delab := whenPPOption getPPCoercions do
+meta def delabSetImageSubtype : Delab := whenPPOption getPPCoercions do
   let #[α, _, f, _] := (← getExpr).getAppArgs | failure
   guard <| f.isAppOfArity ``Subtype.val 2
   let some _ := α.coeTypeSet? | failure

Mathlib/Util/Delaborators.lean

@@ -171,7 +171,7 @@ end existential
 open Lean Lean.PrettyPrinter.Delaborator
 
 /-- Delaborator for `∉`. -/
-@[app_delab Not] def delab_not_in := whenPPOption Lean.getPPNotation do
+@[app_delab Not] def delabNotIn := whenPPOption Lean.getPPNotation do
   let #[f] := (← SubExpr.getExpr).getAppArgs | failure
   guard <| f.isAppOfArity ``Membership.mem 5
   let stx₁ ← SubExpr.withAppArg <| SubExpr.withNaryArg 3 delab

scripts/nolints.json

@@ -4,7 +4,6 @@
  ["defsWithUnderscore", "cfcₙHom_of_cfcHom"],
  ["defsWithUnderscore", "commandSuppress_compilation"],
  ["defsWithUnderscore", "decidableEq_of_subsingleton"],
- ["defsWithUnderscore", "delab_not_in"],
  ["defsWithUnderscore", "equiv_linearIndependent"],
  ["defsWithUnderscore", "exists_delab"],
  ["defsWithUnderscore", "finiteness_nonterminal"],
@@ -458,7 +457,6 @@
  ["defsWithUnderscore", "Set.Icc.convexComb_assoc_coeff₁'"],
  ["defsWithUnderscore", "Set.Icc.convexComb_assoc_coeff₂"],
  ["defsWithUnderscore", "Set.Icc.convexComb_assoc_coeff₂'"],
- ["defsWithUnderscore", "Set.Notation.delab_set_image_subtype"],
  ["defsWithUnderscore", "Set.powersetCard.addActionHom_of_embedding"],
  ["defsWithUnderscore", "Set.powersetCard.addActionHom_singleton"],
  ["defsWithUnderscore", "Set.powersetCard.mulActionHom_compl"],