Fix import format at pandas/tests/io/parser directory
- [x] partial #23334
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Ran `isort --recursive pandas/tests/io/parser` and then checked imports using `isort --recursive --check-only pandas/tests/io/parser`

This PR also exceeded 20 file limit (22 files with setup.cfg), but I think it's acceptable and unnecessary to divide it to two separate PRs.

