Better explanation in using-dev-envs.mdx

[abs007]

I think it should be explicitly mentioned in the Development Environments page that only the docker compose file is being used in the Movies App with Docker Compose section and not the Okteto manifest file and the reason for this should be mentioned too.

In the Movies App with Helm section, it should be mentioned that a helm chart is being used alongside the manifest file in the deploy section of the manifest.

I as a first time visitor think that these changes would help first time users understand the docs better.