Remove @@legendothers_translation.js because it is not used anywhere

I've found this javascript was being loaded and was set as non-cacheable in portal_javascripts. Since this is bad for performance I searched and found out that the javascript is currently useless. It sets a global variable which is not used anywhere. Probably was useful in the past to translate something in javascript.

The main changes are the removal of js_i18n_helper.py and the correspondent entry in jsregistry.xml. However I had to change a lot of extra files due to the rebuild of i18n files and re-ordering of imports to satisfy bin/code-analysis.