DOC:add append example in to_excel documentation
closes #27051


Merged master to hopefully fix CI. Ping on green. @TomAugspurger Looks good now!
Btw, could you explain why the build was failing and merging master to my branch fixed it? :sweat_smile: 
Thanks! Thanks @sameshl 

If there is something broken in master (e.g. a pandas dependency has been updated and it causes a test to fail), then all PRs will fail even if they are correct. So, master needs to be fixed first, and then the fixes in master need to be merged into the PRs that failed. @datapythonista Thanks for the explanation!