refactor: replace wait_for_future with spawn_future for async DataFrame describe method

Author: kosiew

src/dataframe.rs

@@ -476,7 +476,7 @@ impl PyDataFrame {
     /// Calculate summary statistics for a DataFrame
     fn describe(&self, py: Python) -> PyDataFusionResult<Self> {
         let df = self.df.as_ref().clone();
-        let stat_df = wait_for_future(py, df.describe())??;
+        let stat_df = spawn_future(py, async move { df.describe().await })?;
         Ok(Self::new(stat_df))
     }