Removing legacy article because it's no longer needed

Author: Mattp123

powerapps-docs/maker/TOC.yml

@@ -1131,8 +1131,6 @@
           href: ./model-driven-apps/main-form-presentations.md
         - name: Control access to forms
           href: ./model-driven-apps/control-access-forms.md
-        - name: Add a column to a form
-          href: ./model-driven-apps/add-field-form.md
         - name: Show or hide form elements
           href: ./model-driven-apps/visibility-options-legacy.md
         - name: Change navigation within a form