Remove redundant streaming in download of file

In PR #71 a streaming mechanism has been implemented for the endpoint
`/nodes/{nodes_id}/download`, this however is already taken care by
FastAPI StreamingResponse and is therefore redundant and can be removed.

aiida_restapi/config.py

@@ -17,6 +17,3 @@
         'disabled': False,
     }
 }
-
-# The chunks size for streaming data for download
-DOWNLOAD_CHUNK_SIZE = 1024

aiida_restapi/routers/nodes.py

@@ -15,7 +15,6 @@
 from pydantic import ValidationError
 
 from aiida_restapi import models, resources
-from aiida_restapi.config import DOWNLOAD_CHUNK_SIZE
 
 from .auth import get_current_active_user
 
@@ -73,8 +72,7 @@ async def download_node(nodes_id: int, download_format: Optional[str] = None) ->
 
         def stream() -> Generator[bytes, None, None]:
             with io.BytesIO(exported_bytes) as handler:
-                while chunk := handler.read(DOWNLOAD_CHUNK_SIZE):
-                    yield chunk
+                yield from handler
 
         return StreamingResponse(stream(), media_type=f'application/{download_format}')