CLN: Remove unncessary lambda wrapper
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

A lambda wrapper is unnecessary in these cases as the underlying methods are themselves callable. Moreover, the code does not add any logic in the wrapper to warrant the usage of lambda. 