docs: import fastify handler for fastify

Author: enisdenjo

docs/modules/use_fastify.md

@@ -41,7 +41,7 @@ the fastify framework.
 
 ```js
 import Fastify from 'fastify'; // yarn add fastify
-import { createHandler } from 'graphql-http/lib/use/express';
+import { createHandler } from 'graphql-http/lib/use/fastify';
 import { schema } from './my-graphql-schema';
 
 const fastify = Fastify();

src/use/fastify.ts

@@ -28,7 +28,7 @@ export type HandlerOptions<Context extends OperationContext = undefined> =
  *
  * ```js
  * import Fastify from 'fastify'; // yarn add fastify
- * import { createHandler } from 'graphql-http/lib/use/express';
+ * import { createHandler } from 'graphql-http/lib/use/fastify';
  * import { schema } from './my-graphql-schema';
  *
  * const fastify = Fastify();