racket/draw: clean up object name hacks

The only observable impact of this change is that
`the-color-database` will now print as
`(object:color-database% ...)` instead of
`(object:color-database<%> ...)`. The former makes more
sense anyway, given that you can't have an instance of
an interface. If we really want the latter though,
we can add `object-rename` for this purpose.

collects/racket/draw/private/color.rkt

@@ -8,7 +8,7 @@
          color-green
          color-blue
          color-alpha
-         (rename-out [color-database-intf color-database<%>])
+         color-database<%>
          the-color-database
          color->immutable-color)
 
@@ -98,13 +98,10 @@
 
 (define color-objects (make-hash))
 
-(define color-database-intf
-  (let ([color-database<%> (interface ()
-                             find-color
-                             get-names)])
-    color-database<%>))
+(define color-database<%>
+  (interface () find-color get-names))
 
-(defclass* color-database<%> object% (color-database-intf)
+(defclass* color-database% object% (color-database<%>)
   (super-new)
   (def/public (find-color [string? name])
     (let ([name (string-downcase name)])
@@ -120,7 +117,7 @@
   (def/public (get-names)
     (sort (hash-map colors (lambda (k v) k)) string<?)))
 
-(define the-color-database (new color-database<%>))
+(define the-color-database (new color-database%))
 
 (define colors
   #hash(("aliceblue" . #(240 248 255))