DOC: Move import conventions from wiki to docs #30808
- [x] closes #30808
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

@datapythonista I was looking into testing files and there all imports are absolute but previously (according to wiki) explicit relative imports were encouraged. Are absolute imports encouraged in test files also? Lots of people contribute to pandas, so if we don't enforce the policies with validation in the CI, you'll find any possible kind of practice in the code base. I think the preferred option is using absolute imports, so for now, if you can move that policy to the docs, that's a first step. Then, we may considering if its worth detecting relative imports, fixing them, and validating in the CI that they are not reintroduced. Feel free to open an issue to discuss that after this is closed.  @datapythonista, I have updated the docs. Let me know if there should be any changes. Thanks @souvik3333  Thanks both, I deleted the wiki page.