Fix memory leak in Qt event loop integration (#14240) (#14251) The QEventLoop object, `event_loop`, created in `IPython/terminal/pt_intputhooks/qt.py` L58 is not deleted when exiting the scope as passing `app` to the constructor parents the object to `app`. This creates a memory leak as QEventLoop objects are being accumulated. The issue was originally reported by @pag who also suggested the fix. `pytest IPython/terminal/tests/` runs through without errors. I have tested the changes and see no more accumulation of `QEventLoop` objects. This fixes #14240