BOM-2358 : Pyupgrade in dashboard, debug, discussion apps (#26529)

* Python code cleanup by the cleanup-python-code Jenkins job.

This pull request was generated by the cleanup-python-code Jenkins job, which ran
```
cd lms/djangoapps/dashboard; find . -type f -name '*.py' | while read fname; do sed -i 's/  # lint-amnesty, pylint: disable=super-with-arguments//; s/  # lint-amnesty, pylint: disable=import-error, wrong-import-order//; s/  # lint-amnesty, pylint: disable=wrong-import-order//' "$fname"; done; find . -type f -name '*.py' | while read fname; do pyupgrade --exit-zero-even-if-changed --py3-plus --py36-plus --py38-plus "$fname"; done; isort --recursive .
```

The following packages were installed:
`pyupgrade,isort`

* feedback done

Co-authored-by: Zulqarnain <muhammad.zulqarnain@arbisoft.com>