[FIX] mail: Fix crash when adding recipient on mails

When adding more than one recipients on mails a traceback appears.
This was caused because instead of doing a name_get by providing the partners ids as a list, we send them as arguments.
Which wasn't valid because name_get except a single argument.

opw #804691

addons/mail/static/src/js/many2many_tags_email.js

@@ -48,7 +48,7 @@ BasicModel.include({
                 def = self._rpc({
                     model: list.model,
                     method: 'name_get',
-                    args: list.res_ids,
+                    args: [list.res_ids],
                     context: record.getContext({fieldName: fieldName}),
                 });
             }