chore: remove /v1/inference/completion and implementations (#3622)

# What does this PR do?

the /inference/completion route is gone. this removes the
implementations.

## Test Plan

ci

llama_stack/providers/remote/inference/databricks/databricks.py

@@ -9,14 +9,9 @@ from typing import Any
 
 from databricks.sdk import WorkspaceClient
 
-from llama_stack.apis.common.content_types import (
-    InterleavedContent,
-)
 from llama_stack.apis.inference import (
     ChatCompletionResponse,
     ChatCompletionResponseStreamChunk,
-    CompletionResponse,
-    CompletionResponseStreamChunk,
     Inference,
     LogProbConfig,
     Message,
@@ -63,17 +58,6 @@ class DatabricksInferenceAdapter(
     async def shutdown(self) -> None:
         pass
 
-    async def completion(
-        self,
-        model_id: str,
-        content: InterleavedContent,
-        sampling_params: SamplingParams | None = None,
-        response_format: ResponseFormat | None = None,
-        stream: bool | None = False,
-        logprobs: LogProbConfig | None = None,
-    ) -> CompletionResponse | AsyncIterator[CompletionResponseStreamChunk]:
-        raise NotImplementedError()
-
     async def openai_completion(
         self,
         model: str,