read_excel and Excel File Engine conflict
- [x] closes #26566
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry 

cc. @WillAyd 

Note I only decided to raise an error when the engine specified to `read_excel` was different to that of the ExcelFile - otherwise around 15 test cases would need to be changed - let me know what you think
