Colon prefix in bulleted list causes rendering failure

### Describe the bug

Per https://github.com/elastic/docs-builder/pull/2503 if a bulleted list contains a line that starts with a colon, the line fails to render.

I did a simple test in regular docs to confirm this wasn't just a release-note-related issue. For example, I updated the bulleted list in one of the docs-content pages like this:

```md
* A password-based login
* : Log in with Google
* Log in with Microsoft
```
This causes the second line to disappear:

I don't know of a use case off the top of my head where we'd reasonably be starting a line with a colon, but it doesn't seem like a valid reason to fail.

### Expected behavior

The content should be rendered as-is or worst case there should be some sort of warning or error related to the failure.

### Steps to reproduce

1. Find any page that has a bulleted list.
2. Add a colon at the beginning of one of the lines in the list.

### Tooling

- [x] docs-builder
- [ ] migration tooling
- [ ] I'm not sure