chore(python): Fix docstring with_context (#6118)

Author: zundertj

py-polars/polars/internals/lazyframe/frame.py

@@ -2518,7 +2518,8 @@ def with_context(self, other: LDF | list[LDF]) -> LDF:
         │ null │
         └──────┘
 
-        Fill nulls with the median from another dataframe
+        Fill nulls with the median from another dataframe:
+
         >>> train_df = pl.DataFrame(
         ...     {"feature_0": [-1.0, 0, 1], "feature_1": [-1.0, 0, 1]}
         ... ).lazy()