docs: fixed relative link to CONFIG.md (ipfs#3715)

Author: CSDUMMI

docs/MODULE.md

@@ -181,7 +181,7 @@ Enable and configure experimental features.
 |------|---------|
 | object |  [`config-nodejs.js`](https://github.com/ipfs/js-ipfs/blob/master/packages/ipfs-core/src/runtime/config-nodejs.js) in Node.js, [`config-browser.js`](https://github.com/ipfs/js-ipfs/blob/master/packages/ipfs-core/src/runtime/config-browser.js) in browsers |
 
-Modify the default IPFS node config. This object will be *merged* with the default config; it will not replace it. The default config is documented in [the js-ipfs config file docs](./docs/CONFIG.md).
+Modify the default IPFS node config. This object will be *merged* with the default config; it will not replace it. The default config is documented in [the js-ipfs config file docs](./CONFIG.md).
 
 ### `options.ipld`