chore: remove dead code (#3729)

# What does this PR do?
Removing some dead code, found by vulture and checked by claude that
there are no references or imports for these


## Test Plan
CI

llama_stack/providers/utils/memory/openai_vector_store_mixin.py

@@ -296,15 +296,14 @@ class OpenAIVectorStoreMixin(ABC):
     async def shutdown(self) -> None:
         """Clean up mixin resources including background tasks."""
         # Cancel any running file batch tasks gracefully
-        if hasattr(self, "_file_batch_tasks"):
-            tasks_to_cancel = list(self._file_batch_tasks.items())
-            for _, task in tasks_to_cancel:
-                if not task.done():
-                    task.cancel()
-                    try:
-                        await task
-                    except asyncio.CancelledError:
-                        pass
+        tasks_to_cancel = list(self._file_batch_tasks.items())
+        for _, task in tasks_to_cancel:
+            if not task.done():
+                task.cancel()
+                try:
+                    await task
+                except asyncio.CancelledError:
+                    pass
 
     @abstractmethod
     async def delete_chunks(self, store_id: str, chunks_for_deletion: list[ChunkForDeletion]) -> None:

llama_stack/providers/utils/memory/vector_store.py

@@ -20,7 +20,6 @@ from pydantic import BaseModel
 from llama_stack.apis.common.content_types import (
     URL,
     InterleavedContent,
-    TextContentItem,
 )
 from llama_stack.apis.tools import RAGDocument
 from llama_stack.apis.vector_dbs import VectorDB
@@ -129,26 +128,6 @@ def content_from_data_and_mime_type(data: bytes | str, mime_type: str | None, en
         return ""
 
 
-def concat_interleaved_content(content: list[InterleavedContent]) -> InterleavedContent:
-    """concatenate interleaved content into a single list. ensure that 'str's are converted to TextContentItem when in a list"""
-
-    ret = []
-
-    def _process(c):
-        if isinstance(c, str):
-            ret.append(TextContentItem(text=c))
-        elif isinstance(c, list):
-            for item in c:
-                _process(item)
-        else:
-            ret.append(c)
-
-    for c in content:
-        _process(c)
-
-    return ret
-
-
 async def content_from_doc(doc: RAGDocument) -> str:
     if isinstance(doc.content, URL):
         if doc.content.uri.startswith("data:"):