[Data] Fix missing lines in BundleQueue docstring (#48553)

Follow-up to #48503.

---------

Signed-off-by: Balaji Veeramani <bveeramani@berkeley.edu>

python/ray/data/_internal/execution/bundle_queue/bundle_queue.py

@@ -24,6 +24,7 @@ def add(self, bundle: "RefBundle") -> None:
     @abc.abstractmethod
     def pop(self) -> "RefBundle":
         """Remove and return the head of the queue.
+
         Raises:
             IndexError: If the queue is empty.
         """
@@ -32,6 +33,7 @@ def pop(self) -> "RefBundle":
     @abc.abstractmethod
     def peek(self) -> Optional["RefBundle"]:
         """Return the head of the queue without removing it.
+
         If the queue is empty, return `None`.
         """
         ...
@@ -54,6 +56,7 @@ def estimate_size_bytes(self) -> int:
     @abc.abstractmethod
     def is_empty(self):
         """Return whether this queue and all of its internal data structures are empty.
+
         This method is used for testing.
         """
         ...