Remove unused SimpleForm scaffold template.

lib/templates/erb/scaffold/_form.html.erb

@@ -1,14 +0,0 @@
-<%# frozen_string_literal: true %>
-<%%= simple_form_for(@<%= singular_table_name %>) do |f| %>
-  <%%= f.error_notification message: f.object.errors[:base].to_sentence if f.object.errors[:base].present? %>
-
-  <div class="form-inputs">
-  <%- attributes.each do |attribute| -%>
-    <%%= f.<%= attribute.reference? ? :association : :input %> :<%= attribute.name %> %>
-  <%- end -%>
-  </div>
-
-  <div class="form-actions">
-    <%%= f.button :submit %>
-  </div>
-<%% end %>