[Bug] Fix dataset path check in Table::open (#326)

Fixed a bug that prevents to open remote tables.

python/lancedb/table.py

@@ -534,7 +534,9 @@ class LanceTable(Table):
     @classmethod
     def open(cls, db, name):
         tbl = cls(db, name)
-        if not os.path.exists(tbl._dataset_uri):
+        fs, path = pa.fs.FileSystem.from_uri(tbl._dataset_uri)
+        file_info = fs.get_file_info(path)
+        if file_info.type != pa.fs.FileType.Directory:
             raise FileNotFoundError(
                 f"Table {name} does not exist. Please first call db.create_table({name}, data)"
             )