Update build time env variable link in the runtime config section (#1…

…7017)

Since [the current link](https://nextjs.org/docs/api-reference/next.config.js/environment-variables) for the build-time environment variables docs recommends the approach outlined in [this section](https://nextjs.org/docs/basic-features/environment-variables), I think the link should point there instead.

docs/api-reference/next.config.js/runtime-configuration.md

@@ -4,7 +4,7 @@ description: Add client and server runtime configuration to your Next.js app.
 
 # Runtime Configuration
 
-> Generally you'll want to use [build-time environment variables](/docs/api-reference/next.config.js/environment-variables.md) to provide your configuration. The reason for this is that runtime configuration adds rendering / initialization overhead and is incompatible with [Automatic Static Optimization](/docs/advanced-features/automatic-static-optimization.md).
+> Generally you'll want to use [build-time environment variables](/docs/basic-features/environment-variables.md) to provide your configuration. The reason for this is that runtime configuration adds rendering / initialization overhead and is incompatible with [Automatic Static Optimization](/docs/advanced-features/automatic-static-optimization.md).
 
 To add runtime configuration to your app open `next.config.js` and add the `publicRuntimeConfig` and `serverRuntimeConfig` configs: