rewrite dict as literal in tests/io/parser/test_index_col.py
for issue # 38138 
rewrite unnecessary dict call as a literal in pandas/tests/io/parser/test_index_col.py

Please let me know if anything needs to be amended, changed or fixed. I'm new to contributing.

- [ ] issue #38138 
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @pillemer! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2020-12-07 04:33:22 UTC Thanks. Could you fix up the linting errors? @mroeschke, no problem, done! Is there anything else? > @mroeschke, no problem, done! Is there anything else?

There's still some failures, could you try again please? 
```
pre-commit run --files pandas/tests/io/parser/test_index_col.py
``` closing as it looks like this one's already been done, sorry about that