Use consistent comment style in `default.json` (#25783)

This PR updates the comments in the `default.json` file consistently use
`//`.

Some comments were using `///`, which doesn't make sense in JSONC.

Release Notes:

- N/A
6f30d5da71Marshall Bowers committed on 2/27/2025, 10:50:23 PM· committed by GitHubparentb8387c6
1 file changedLine totals unavailable