Fixed Docker version with Ollama

[mrepetto-certx]

Given that we have Ollama as the new recommended setup, I propose to make a modification to the Dockerfile and compose it to make it coherent with the new local setup. I decoupled Ollama from privateGPT, making it a separate microservice.

[imartinez]

Makes total sense, thanks!

[qdm12]

Makes total sense, thanks!

Ehh we should really stop adding things to that poetry extras command. I don't use Ollama and now the default Docker image comes with Ollama extras I have no use for. We should either bundle ALL extras, or none at all in my opinion (see below how this would work).
I opened PR #1792 to have a build argument POETRY_EXTRAS so that you can build your Docker image with --build-arg POETRY_EXTRAS="..." as you wish. If we're ok with breaking compatibility still, I think it would be wise to have default to an empty string POETRY_EXTRAS="" and document what extras are available for docker build commands.