Currently, only stable releases see their translations updated. This has
resulted in master accumulating outdated stuff for years, which can be
confusing for users testing master on runbot.
This one-shot commit resynchronizes master translations based on the
content from 16.0 and removes empty PO files (i.e. no longer containing
translations).
closesodoo/odoo#121629
Related: odoo/enterprise#41171
Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>