[FIX] base: do not put mockup class in future registries

Followup of #82838 and #82844

By default, every subclass of BaseModel is registered in a mapping for
the automatic discovery of model classes by registries.  Prevent
registration of the mockup class used for rendering the database manager
templates.

closes odoo/odoo#83626

X-original-commit: 3bce74b20f8c15befee453382e3ab4697bee6960
Signed-off-by: Raphael Collet <rco@odoo.com>

odoo/addons/base/models/ir_qweb.py

@@ -376,7 +376,7 @@ def render(template_name, values, load, **options):
         _Registry__cache = {}
 
     class MockIrQWeb(IrQWeb):
-        _name = 'ir.qweb.mock'
+        _register = False               # not visible in real registry
 
         pool = MockPool()