TST: GH24798 df.replace() with duplicate columns
- [x] xref #24798 
- [x] tests added / passed
- [x] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

thanks @matteosantama 

I don't think this completely closes #24798 ?