DOC: Fix EX02 in pandas.Series.memory_usage
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Related to #27977. 

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I think for now should just stick with what CI is yielding. I don't think the 8 byte difference is worth worrying too much about, though if you see something more problematic feel free to open an issue for it.

Thanks anyway for the PR!