[FIX] base: prevent copying of contact tag partners

before this commit, on duplicating a contact tag
will duplicate the assigned partners also.

suppose if we have a partner A with tag B assigned,
and then we duplicate tag B and create new tag C,
the newly created tag is automatically getting
assigned to partner A.

after this commit, the copy is set to False for
partner_ids field in tag and then the partners
wont be copied on duplicating a tag

closes odoo/odoo#118947

X-original-commit: 5dc9104403606b6421b9cde732cfa3d6bb5962aa
Signed-off-by: Julien Castiaux (juc) <juc@odoo.com>