%prun: Restore `stats.stream` after running `print_stream`. When profiling, the output from `print_stream` is captured so that the output can be paged. To do so, the `stream` attribute is set to a `StringIO` object but was not restored after the output was captured. As a result, the stats object returned by `%prun -r` did not display any output when calling its `print_stream` method. In addition, the `pstats.Stats` class has the `stream` attribute for all currently supported Python versions, so the extra branch of code can be removed.