Stop returning 0 in cmp_comparison_test

cmp_comparison_test has no return value and should thus not return 0.

tests/tcctest.c

@@ -2596,7 +2596,6 @@ void cmp_comparison_test(void)
   s.b1 = 1;
   glob1 = 42; glob2 = 42;
   s.b2 = 0;
-  glob3 = 43;
   glob3 = 43;
   compare_comparisons (&s);
 }