Update README.md

Author: samchungy

README.md

@@ -811,7 +811,7 @@ As an example `z.string().nullable()` will be rendered differently
   - `prefixItems` mapping for OpenAPI 3.1.0+
 - ZodUndefined
 - ZodUnion
-  - By default it outputs an `allOf` schema. Use `unionOneOf` to change this to output `oneOf` instead.
+  - By default it outputs an `anyOf` schema. Use `unionOneOf` to change this to output `oneOf` instead.
 - ZodUnknown
 
 If this library cannot determine a type for a Zod Schema, it will throw an error. To avoid this, declare a manual `type` in the `.openapi()` section of that schema.