Revert "form: add number to section headers"

This reverts commit f42977e40a.

app/models/champs/header_section_champ.rb

@@ -2,11 +2,4 @@ class Champs::HeaderSectionChamp < Champ
   def search_terms
     # The user cannot enter any information here so it doesn’t make much sense to search
   end
-
-  def section_index
-    dossier
-      .champs
-      .filter { |c| c.type_champ == TypeDeChamp.type_champs.fetch(:header_section) }
-      .index(self) + 1
-  end
 end