[BUG] Sentence-level instances of the `tech preview` tag

In the Asciidoc system, you can use [inline tags](https://docs.elastic.dev/migration/syntax/beta-dev-and-preview#inline-notes) to mark functionality as being in a pre-release state. There's no equivalent in V3 at the moment, so the tech preview tag has been hardcoded in as a temporary workaround (potentially the beta and dev tags as well). [Here's](https://staging-website.elastic.co/docs/solutions/security/investigate/open-manage-cases#cases-ui-open) an example of the tech preview tag hardcoded into Security case docs:

Here are some additional instances of the hard-coded `[preview]` tag in other docs:
- https://github.com/elastic/docs-content/blob/main/explore-analyze/alerts-cases/cases.md
- https://github.com/elastic/docs-content/blob/main/explore-analyze/alerts-cases/alerts/alerting-common-issues.md
- https://github.com/elastic/docs-content/blob/main/explore-analyze/alerts-cases/alerts/alerting-troubleshooting.md
- https://github.com/elastic/docs-content/blob/main/explore-analyze/alerts-cases/alerts/create-manage-rules.md
- https://github.com/elastic/docs-content/blob/main/explore-analyze/alerts-cases/alerts/rule-action-variables.md

For now, we plan to leave the tags as they are. Removing them is not a viable option as it would delete important information. Moving forward, we should discuss a standard way of handling them and potentially supporting prose-level labeling for functionality in non-GA states.