refactor: remove container from list of run image types

[Bobbins228]

What does this PR do?

[Provide a short summary of what this PR does and why. Link to relevant issues if applicable.] Removes the ability to run llama stack container images through the llama stack CLI Closes #2110

Test Plan

[Describe the tests you ran to verify your changes with result summaries. Provide clear instructions so the plan can be easily re-executed.] Run:

llama stack run /path/to/run.yaml --image-type container

Expected outcome:

llama stack run: error: argument --image-type: invalid choice: 'container' (choose from 'conda', 'venv')