The debugger mode of %run escapes the boundaries of a file

## Steps to reproduce

* Create a `test.py` file with the contents `a = 5` in the current directory
* Execute `%run -d test.py`
* Start executing `s` (step) commands in the debugger

## Expected result
The debugger terminates after two steps, when the `test.py` script exits.

## Actual result
The debugger carries on going through IPython's internals.

## System info
Manjaro Linux, Python 3.9.4, IPython 7.22.0 (reproduces on IPython 8.0.0.dev)