ref link: don't match if new line between `:` and URL.

[jorgeorpinel]

*   content/docs/user-guide/experiment-management/hydra-composition.md
   *   `yaml = https://`yaml/ (Site not found)

1/28 links failed.

Any idea where this comes from? Seems like a regexp 🐞 to me (see src).

U: Ah yeah, I think it's from

... [defaults list]:

```yaml

• [ ] So the regexp should not match ref links with an empty line between : and the URL.

Originally posted by @jorgeorpinel in https://github.com/iterative/dvc.org/issues/4041#issuecomment-1276969824

[jorgeorpinel]

p.s. fix needed ATM for https://github.com/iterative/dvc.org/pull/4041 to pass checks.