style: Consistently use double quotes for strings in duckdb_handler and connection_args

Author: parthiv11

mindsdb/integrations/handlers/duckdb_handler/connection_args.py

@@ -24,4 +24,4 @@
     database="sample_data",
     read_only=True,
     motherduck_token="ey...enKoT.SsEcCa......",
-)
+)

mindsdb/integrations/handlers/duckdb_handler/duckdb_handler.py

@@ -168,4 +168,4 @@ def get_columns(self, table_name: str) -> Response:
         """
 
         query = f"DESCRIBE {table_name};"
-        return self.native_query(query)
+        return self.native_query(query)