A laptop is required for both in-person and online trainings

### How could the content be improved?

In the [Preparing for your Training section](https://carpentries.github.io/instructor-training/index.html#preparing-for-your-training), we include this item for inperson training, but it should apply to online training as well. (Also numbered list formatting needs to be fixed.)

> Please also bring a laptop powerful enough to teach on so that you can take part in all of the practical exercises (a tablet will not be sufficient).

### Which part of the content does your suggestion apply to?

https://carpentries.github.io/instructor-training/index.html#preparing-for-your-training

Open the Preparing for your Training section at the linked Instructor Training page and review the laptop requirement and numbered list formatting. Update the content so the requirement applies to both in-person and online training, and confirm the numbered list renders correctly.

Written by the indexing model from the issue text.