tech(clean): remove Column classname: attribute

Co-authored-by: mfo <mfo@users.noreply.github.com>

app/components/instructeurs/column_table_header_component.rb

@@ -9,6 +9,12 @@ class Instructeurs::ColumnTableHeaderComponent < ApplicationComponent
 
   private
 
+  def classname(column)
+    return 'status-col' if column.dossier_state?
+    return 'number-col' if column.type == :number
+    return 'sva-col' if column.column == 'sva_svr_decision_on'
+  end
+
   def update_sort_path(column)
     id = column.id
     order = opposite_order_for(column)