Fix broken async reference file system _cat_file method

Author: mpiannucci

fsspec/implementations/reference.py

@@ -803,7 +803,7 @@ async def _cat_file(self, path, start=None, end=None, **kwargs):
             return part_or_url[start:end]
         protocol, _ = split_protocol(part_or_url)
         try:
-            await self.fss[protocol]._cat_file(part_or_url, start=start, end=end)
+            return await self.fss[protocol]._cat_file(part_or_url, start=start, end=end)
         except Exception as e:
             raise ReferenceNotReachable(path, part_or_url) from e