refactor: remove Conda support from Llama Stack (#2969)

# What does this PR do?
<!-- Provide a short summary of what this PR does and why. Link to
relevant issues if applicable. -->
This PR is responsible for removal of Conda support in Llama Stack

<!-- If resolving an issue, uncomment and update the line below -->
<!-- Closes #[issue-number] -->
Closes #2539

## 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.* -->

llama_stack/templates/meta-reference-gpu/build.yaml

@@ -28,8 +28,7 @@ distribution_spec:
     - provider_type: remote::tavily-search
     - provider_type: inline::rag-runtime
     - provider_type: remote::model-context-protocol
-image_type: conda
-image_name: meta-reference-gpu
+image_type: venv
 additional_pip_packages:
 - aiosqlite
 - sqlalchemy[asyncio]

llama_stack/templates/meta-reference-gpu/doc_template.md

@@ -58,7 +58,7 @@ $ llama model list --downloaded
 
 ## Running the Distribution
 
-You can do this via Conda (build code) or Docker which has a pre-built image.
+You can do this via venv or Docker which has a pre-built image.
 
 ### Via Docker
 
@@ -92,12 +92,12 @@ docker run \
   --env SAFETY_MODEL=meta-llama/Llama-Guard-3-1B
 ```
 
-### Via Conda
+### Via venv
 
 Make sure you have done `uv pip install llama-stack` and have the Llama Stack CLI available.
 
 ```bash
-llama stack build --template {{ name }} --image-type conda
+llama stack build --template {{ name }} --image-type venv
 llama stack run distributions/{{ name }}/run.yaml \
   --port 8321 \
   --env INFERENCE_MODEL=meta-llama/Llama-3.2-3B-Instruct