DOC: Fix incorrect doc string for infer_dtype (#38375)
- [x] closes #38375
- ~~tests added / passed~~
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- ~~whatsnew entry~~

A minor fix to https://github.com/pandas-dev/pandas/issues/38375 correcting the output of an example in `infer_dtype` doc string
