eval-with: Explicitly say that the evaluation happens in a fresh namespace.

utils.rkt

@@ -81,8 +81,8 @@
           x))))
 
 ;;; Temporarily injects the mappings from the given hash table as
-;;; bindings in the current namespace and then evaluates the
-;;; expression.
+;;; bindings in a namespace including racket/base and then evaluates
+;;; the expression.
 ;;;
 ;;; > (let ([ht #hash((a . 1) (b . 1))])
 ;;;     (eval-with ht '(+ b a 1)))