Fix link markdown used by the doc builds in annotations.yml (#2579)

## Changes
- Fix link markdown in annotations.yml
- Edits to the artifacts dynamic_version setting description

## Why
annotations.yml is used by the bundle docgen tool to generate Markdown
files for the docs site. But since our recent migration, the markdown
for links with dynamically generated link text needs to have the
underscore escaped.

## Tests
Peer review, testing the generated *.md in a docs PR:
https://github.com/databricks-eng/universe/pull/987364

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Co-authored-by: Ilya Kuznetsov <ilya.kuznetsov@databricks.com>

Author: juliacrawf-db