Revert "add hash->list-lens and list->hash-lens"

This reverts commit d10c85480f56bfe2c36cdd74be0476894b6803bd.

unstable/lens/isomorphism.scrbl

@@ -49,7 +49,6 @@ example, are defined like this:
 @deflenses[[string->symbol-lens symbol->string-lens
             number->string-lens string->number-lens
             list->vector-lens vector->list-lens
-            list->string-lens string->list-lens
-            hash->list-lens list->hash-lens]]{
+            list->string-lens string->list-lens]]{
 Isomorphim lenses for @racket[string->symbol], @racket[number->string], and so on.
 }

unstable/lens/isomorphism/base.rkt

@@ -10,7 +10,6 @@
            number->string-lens string->number-lens
            list->vector-lens vector->list-lens
            list->string-lens string->list-lens
-           hash->list-lens list->hash-lens
            ))
 
 (require racket/match
@@ -44,8 +43,6 @@
     (isomorphism-lenses list->vector vector->list))
   (define-values [list->string-lens string->list-lens]
     (isomorphism-lenses list->string string->list))
-  (define-values [hash->list-lens list->hash-lens]
-    (isomorphism-lenses hash->list make-immutable-hash))
   )
 
 (module+ test