docs: fix refine fn to encode works properly (#5148)

Author: imranbarbhuiya

packages/docs/content/codecs.mdx

@@ -191,7 +191,7 @@ During regular decoding, a `ZodPipe<A, B>` schema will first parse the data with
 All checks (`.refine()`, `.min()`, `.max()`, etc.) are still executed in both directions. 
 
 ```ts
-const schema = stringToDate.refine((date) => date.getFullYear() > 2000, "Must be this millenium");
+const schema = stringToDate.refine((date) => date.getFullYear() >= 2000, "Must be this millenium");
 
 schema.encode(new Date("2000-01-01"));
 // => Date