Include zero-width-space in string-normalize.

Closes PR 12683.

collects/framework/private/text.rkt

@@ -922,7 +922,8 @@
              normalize?))]
         [else
          (preferences:get 'framework:do-paste-normalization)]))
-    (define/public (string-normalize s) (string-normalize-nfkc s))
+    (define/public (string-normalize s) 
+      (regexp-replace* #rx"\u200b" (string-normalize-nfkc s) ""))
     
     (define/override (do-paste start time)
       (dynamic-wind

collects/scribblings/framework/text.scrbl

@@ -383,7 +383,10 @@
   }
 
   @defmethod[(string-normalize [s string?]) string?]{
-    Normalizes @racket[s]. Defaults to @racket[string-normalize-nfkc].
+    Normalizes @racket[s]. Defaults to:
+    @racketblock[(regexp-replace* #rx"\u200b"
+                                  (string-normalize-nfkc s)
+                                  "")]
   }
 
 }