factor: remove IF_LINT

* src/factor.c (factor_using_squfof) [USE_SQUFOF]:
Use plain assert (...), not IF_LINT (assert (...)).
This code is currently never compiled or executed,
so this is merely a symbolic cleanup.

src/factor.c

@@ -2076,7 +2076,7 @@ factor_using_squfof (uintmax_t n1, uintmax_t n0, struct factors *factors)
           div_smallq (q, rem, S + P, Q);
           P1 = S - rem; /* P1 = q*Q - P */
 
-          IF_LINT (assert (q > 0 && Q > 0));
+          assert (q > 0 && Q > 0);
 
 # if STAT_SQUFOF
           q_freq[0]++;