Fix wrong url for upload

When trying to complete the travel expenses workflow from https://github.com/nuxeo/marketplace-travel-expenses.

When selecting a file to attach. The nuxeo client is POSTing on:

http://localhost:8080/nuxeo/site/api/v1/automation/upload

which is wrong, it should simply be http://localhost:8080/nuxeo/site/api/v1/automation.