Revert inconsistent changes from _meth to meth (#4051)

Signed-off-by: Deepyaman Datta <deepyaman.datta@utexas.edu>

kedro/io/lambda_dataset.py

@@ -49,15 +49,15 @@ def _to_str(func: Any) -> str | None:
 
         return descr
 
-    def load(self) -> Any:
+    def _load(self) -> Any:
         if not self.__load:
             raise DatasetError(
                 "Cannot load data set. No 'load' function "
                 "provided when LambdaDataset was created."
             )
         return self.__load()
 
-    def save(self, data: Any) -> None:
+    def _save(self, data: Any) -> None:
         if not self.__save:
             raise DatasetError(
                 "Cannot save to data set. No 'save' function "