Update environment-variables.mdx

Changed additional instance of npm exec

docs/pages/guides/environment-variables.mdx

@@ -39,7 +39,7 @@ AUTH_SECRET="This is an example"
 `AUTH_SECRET` is a random token used by the library to encrypt tokens and email verification hashes, and it's mandatory to keep things secure (See [Deployment](/getting-started/deployment) to learn more). You can use the CLI to generate an auth secret:
 
 ```bash npm2yarn
-npm exec auth secret
+npx auth secret
 ```
 
 ## Environment Variable Inference