rs: Switch to #lang racket, but keep the types where they work.

rs-tests.rkt

@@ -1,8 +1,8 @@
-#lang typed/racket
+#lang racket
 
 ;;; Tests for dds/rs.
 
-(require typed/rackunit "rs.rkt")
+(require rackunit "rs.rkt")
 
 (test-case "Basic definitions"
   (let* ([r1 (reaction (set 'x) (set 'y) (set 'z))]

rs.rkt

@@ -1,11 +1,12 @@
-#lang typed/racket
+#lang racket
+
+(require typed/racket)
 
 ;;; dds/rs
 
 ;;; Definitions for working with reaction systems.
 
-(require/typed "utils.rkt"
-  [string->any (String -> Any)])
+(require "utils.rkt")
 
 (provide
  ;; Structures