Fix 1 occurrence of if-else-false-to-and

This `if` expression can be refactored to an equivalent expression using `and`.

Author: resyntax-ci[bot]

typed-racket-lib/typed-racket/static-contracts/combinators/function.rkt

@@ -149,7 +149,7 @@
   (and (and (not rest-arg) (null? (append mand-kw-args mand-args opt-kw-args opt-args)) typed-side?)
        ;; currently we only handle this trivial case
        ;; we could probably look at the actual kind of `range-args` as well
-       (if (not range-args) 'flat #f)))
+       (and (not range-args) 'flat)))
 
 
 (define (function-sc-constraints v f)