fix(core): accept kwargs in get file

Fixes iterative/dvc-s3#80

It is similar to `gcsfs` and `adlfs`.

On our end it seems `max_concurrency` is passed here https://github.com/iterative/dvc-objects/blob/main/src/dvc_objects/fs/generic.py#L210 and since the new version has this attr we pass it now, which most likely leads to this error.

I'm not sure why `_gef_file` part was not yet implemented. @pmrowla might have a better idea on was it complicated, or less priority. It seems it is the natural next step to do so.

s3fs/core.py

@@ -1271,7 +1271,7 @@ async def _upload_chunk(chunk, part_number):
         return out
 
     async def _get_file(
-        self, rpath, lpath, callback=_DEFAULT_CALLBACK, version_id=None
+        self, rpath, lpath, callback=_DEFAULT_CALLBACK, version_id=None, **kwargs
     ):
         if os.path.isdir(lpath):
             return