test: fix dummy app
test: fix dummy app

See https://github.com/rails/sprockets-rails/issues/444.

Signed-off-by: Pierre-Alexandre Meyer <ff019a5748a52b5641624af88a54a2f0e46a9fb5@mouraf.org>

killbill/killbill-avatax-ui,killbill/killbill-avatax-ui,killbill/killbill-avatax-ui,killbill/killbill-avatax-ui