fix(spp_registry): fix Registrant Tags EvalError on ref() in context

The Registrant Tags action used ref() in the context field body which is
evaluated client-side in Odoo 19 where ref() is not available. Move to
eval attribute which is processed server-side during XML loading.

Fixes #879

Author: emjay0921

spp_registry/views/tags_view.xml

@@ -15,7 +15,8 @@
         >[('namespace_uri', '=', 'urn:openspp:vocab:registrant-tags')]</field>
         <field
             name="context"
-        >{'default_vocabulary_id': ref('spp_registry.vocab_registrant_tags')}</field>
+            eval="{'default_vocabulary_id': ref('spp_registry.vocab_registrant_tags')}"
+        />
         <field name="help" type="html">
             <p class="o_view_nocontent_smiling_face">
                 Add a Registrant Tag!