Revert "Add spree namespace to the locales"

I think the Spree.t helper was created so that we don't need to add the
spree namespace explicitly on every locale file. Once current i18n
branch in spree/spree gets into master we can just update all t() to use
Spree.t() instead

This reverts commit bd72fec3fef686bbae92ae9e9e46595e74ca9ab3.