[FIX] Update spacing to fix list rendering

[kabilar]

The list on the schema webpage does not render correctly due to a minor spacing issue in the markdown file:

cc @satra @ayendiki

[effigies]

This page was never intended to be rendered as part of the specification, and it was removed from the mkdocs build in #2241 (see https://bids-specification.readthedocs.io/en/latest/schema/index.html).

The places it needs to render are:

• https://github.com/bids-standard/bids-specification/blob/master/src/schema/README.md
• https://bidsschematools.readthedocs.io/en/latest/description.html

Are there other places you know of?

[kabilar]

Sounds good. I am not aware of any other places. Will go ahead and close.