Fix crash on attributes with interpolation arguments

The application crashed when we generated hints to attributes with
interpolation arguments in their `human_attribute_name`.

When generating the hint, we used the `custom_label` method to generate
a label and get the `for` attribute and, since we weren't passing a
text, it used the default human attribute name for the field. However,
it crashes if the default attribute name requires an interpolation
argument.

So now, since we were only using the `custom_label` method in order to
get the `for` attribute, we're simply passing an arbitrary text to the
method.

lib/consul_form_builder.rb

@@ -83,7 +83,7 @@ class ConsulFormBuilder < FoundationRailsHelper::FormBuilder
 
     def help_text_id(attribute, options)
       if options[:hint].present?
-        "#{custom_label(attribute, nil, nil).match(/for="([^"]+)"/)[1]}-help-text"
+        "#{custom_label(attribute, "Example", nil).match(/for="([^"]+)"/)[1]}-help-text"
       end
     end
 end