Rewrite dict literal for files in pandas/tests/frame/test_indexing and test_where 
- [ ] closes #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 in two spots:
- pandas/tests/frame/test_indexing
- pandas/tests/frame/test_where 
based on @jreback comments:
https://github.com/pandas-dev/pandas/pull/38207#issuecomment-736960208