Fix soundness issue of missing premises for count bag lemmas (#7615)

Fix soundness issue of missing premises for count bag lemmas (#7615)

This PR fixes soundness issues found by cvc5 fuzzy sygus when it answers unsat for sat problems.
The error is related to a previous fix which did not include the required antecedent in the two lemmas:

(=>  (= e x)
        (=
              (bag.count e (bag x c))
             (ite (>= c 1) c 0)))

and

(=>  (distinct x e))  (= (bag.count e (bag x c)) 0))