The overtaking=no is good, but the restriction=no_u_turn https://wiki.openstreetmap.org/wiki/Tag:restriction=no_u_turn needs to go on a relation object which has to/from/via members, and not on the way.

In JOSM add a new relation, set the tags type=relation + relation=no_u_turn then add the two ways as to/from members and the intersection node which connects both as a via member.