refactor: remove container from list of run image types (#2178)

# 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')
```

[//]: # (## Documentation)

llama_stack/distribution/utils/exec.py

@@ -23,11 +23,8 @@ from llama_stack.distribution.utils.image_types import LlamaStackImageType
 
 def formulate_run_args(image_type, image_name, config, template_name) -> list:
     env_name = ""
-    if image_type == LlamaStackImageType.CONTAINER.value:
-        env_name = (
-            f"distribution-{template_name}" if template_name else (config.container_image if config else image_name)
-        )
-    elif image_type == LlamaStackImageType.CONDA.value:
+
+    if image_type == LlamaStackImageType.CONDA.value:
         current_conda_env = os.environ.get("CONDA_DEFAULT_ENV")
         env_name = image_name or current_conda_env
         if not env_name: