docs(python): use public API to consume stream handle (apache#2105)

Small follow-up on apache#2097

This method is available starting from pyarrow 15.0, only one release
after introduction of the general protocol, so I think it should be fine
to just use that.

docs/source/python/recipe/driver_manager_lowlevel.py

@@ -58,7 +58,7 @@
 #: (other drivers, like the PostgreSQL driver, may know).
 assert rowcount == -1
 #: We can use the PyArrow APIs to read the result.
-reader = pyarrow.RecordBatchReader._import_from_c_capsule(handle.__arrow_c_stream__())
+reader = pyarrow.RecordBatchReader.from_stream(handle)
 assert reader.schema == pyarrow.schema([("THEANSWER", "int64")])
 #: Finally, we have to clean up all the objects.  (They also support the
 #: context manager protocol.)