docs: correct migration.md wording — completion path is internalized, not obsolete

Author: felixweinberger

docs/migration.md

@@ -269,7 +269,7 @@ This applies to:
 | `schemaToJson(schema)` | `standardSchemaToJsonSchema(schema)` |
 | `parseSchemaAsync(schema, data)` | `validateStandardSchema(schema, data)` |
 | `SchemaInput<T>` | `StandardSchemaWithJSON.InferInput<T>` |
-| `getSchemaShape`, `getSchemaDescription`, `isOptionalSchema`, `unwrapOptionalSchema` | No replacement — these were Zod introspection helpers for the now-obsolete completion path |
+| `getSchemaShape`, `getSchemaDescription`, `isOptionalSchema`, `unwrapOptionalSchema` | No replacement — these are now internal Zod introspection helpers |
 
 ### Host header validation moved