[Breaking] Remove deprecated `publicRuntimeConfig` and `serverRuntimeConfig` (#83944)
This PR removed the deprecated runtime configs.
https://github.com/vercel/next.js/blob/74b226fe4afc7149901affc3c005476e9e592315/docs/02-pages/04-api-reference/04-config/01-next-config-js/runtime-configuration.mdx#L6-L8
This way, we can use the serialized next config for the prod server.