Fix error in second code snippet under Server Functions with Actions (#7414)

Author: hyundonmoon

src/content/reference/rsc/server-functions.md

@@ -137,7 +137,7 @@ function UpdateName() {
   return (
     <form action={submitAction}>
       <input type="text" name="name" disabled={isPending}/>
-      {state.error && <span>Failed: {state.error}</span>}
+      {error && <span>Failed: {error}</span>}
     </form>
   )
 }