[Data] Update Dataset.zip() docs (#46757)

Update Dataset.zip() docs to remove incorrect statement about materializing the dataset
Fix ExecutionPlan.__repr__() string typo

Signed-off-by: Scott Lee <sjl@anyscale.com>

python/ray/data/_internal/plan.py

@@ -96,6 +96,7 @@ def __repr__(self) -> str:
             f"ExecutionPlan("
             f"dataset_uuid={self._dataset_uuid}, "
             f"snapshot_operator={self._snapshot_operator}"
+            f")"
         )
 
     def get_plan_as_string(self, dataset_cls: Type["Dataset"]) -> str:

python/ray/data/dataset.py

@@ -2256,7 +2256,7 @@ def sort(
 
     @PublicAPI(api_group=SMD_API_GROUP)
     def zip(self, other: "Dataset") -> "Dataset":
-        """Materialize and zip the columns of this dataset with the columns of another.
+        """Zip the columns of this dataset with the columns of another.
 
         The datasets must have the same number of rows. Their column sets are
         merged, and any duplicate column names are disambiguated with suffixes like
@@ -2277,8 +2277,6 @@ def zip(self, other: "Dataset") -> "Dataset":
             >>> ds1.zip(ds2).take_batch()
             {'id': array([0, 1, 2, 3, 4]), 'id_1': array([0, 1, 2, 3, 4])}
 
-        Time complexity: O(dataset size / parallelism)
-
         Args:
             other: The dataset to zip with on the right hand side.