Before this commit, there is no way to "void" model translations, i.e.,
discard a translation and let the value fall back on the 'en_US' value.
The API of methods write() and update_field_translations() can only
overwrite the translations for the specified languages.
After this commit, calling update_field_translations() with a falsy
value except the empty string discards the corresponding translation
value, and let the value of the field in the given language fall back on
the 'en_US' value of the field.
X-original-commit: 5434fb845c393327db377abf872c448f4860a7d3
Part-of: odoo/odoo#111869
Chong Wang (cwg)
4e282f10fc