Rewrite dict literal for files in tests/groupby & ./pandas/tests/dtypes 
- [ ] xref #38138
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
identify unnecessary dict call - rewrite as a literal
Rewrites as dictionary literals for the following files:

 ./pandas/tests/dtypes/test_inference.py
./pandas/tests/groupby/test_function.py
./pandas/tests/groupby/transform/test_transform.py


Hello @Qbiwan! 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 2020-12-01 13:35:16 UTC Thanks @Qbiwan - looks like there's some pre-commit failures, can you fix them up?
```
pre-commit run --files pandas/tests/dtypes/test_inference.py pandas/tests/groupby/test_function.py pandas/tests/groupby/transform/test_transform.py
``` @MarcoGorelli thanks, i think it is passing pre-commit now