[Bug]: Update Basic Auth instructions in docs

[Flowko]

Description

since https://github.com/coollabsio/coolify/releases/tag/v4.0.0-beta.262 was released, my envirment stopped working, took me some time to figure it out, but found that its due to the double dollar signs i had in my labels, updating them to be single dollar signs fixed it, better to update the docs as well so people can use the working version from now on, Thanks

https://coolify.io/docs/knowledge-base/traefik/basic-auth

Minimal Reproduction (if possible, example repository)

Follow the Basic Auth instruction at https://coolify.io/docs/knowledge-base/traefik/basic-auth

Exception or Error

No response

Version

v4.0.0-beta.265