[I18N] bg.po: properly translate New

For some reason, “New” has been translated as “Nieuw” in Bulgarian, but
this is not Bulgarian, this is Dutch.

This commit replaces all occurrences of “Nieuw” with “Нов”, which is the
correct translation for “New” in Bulgarian.

closes odoo/odoo#133621

X-original-commit: 73512e95
Related: odoo/enterprise#46568
Signed-off-by: Louis Wicket (wil) <wil@odoo.com>