Minor refactor to support_form_with implementation

Realizing that, with the keyword argument spread syntax, I don't need
to do merging, I can just. spread at the right place!

My rationale for the ordering here is: if the caller theoretically tried
to override the builder (even though I don't see why), I think we would
want to respect that. Whereas the `class` argument should be overridden
because we're safely *merging* our `.support-form` class into it.

app/helpers/support_form_helper.rb

@@ -50,10 +50,11 @@ module SupportFormHelper
 	end
 
 	def support_form_with(**options, &block)
-		options.merge!(
+		form_with(
 			builder: SupportFormBuilder,
+			**options,
 			class: ["support-form", options[:class]],
+			&block
 		)
-		form_with(**options, &block)
 	end
 end