fix(documentation/user_guides/indexing): Highlight `where`, add Todo for "wrong" example
- [X] add Todo marker for "wrong" example (description said `where` should be used but actually it isn't)
- [ ] add actual example using `where` (beyond my skillset)


I am not sure this is worth merging with the TODO. you are welcome to actually change to what you believe is the correct docs. I understand, but I actually was looking at this part of the docs, because I don't know how to do it... 🤷 Thanks @JoeSchr for the PR. rather than the TODO, if not fixing, maybe open an issue describing the problem instead. That would have more visibility.