Update Allure ScalaTest documentation and example

**Pre-check**
- [x] I'm aware that I can [edit the docs](https://github.com/allure-framework/allure-docs/) and submit a pull request

**Describe the improvement**

I'd like to report
- [x] Unclear documentation
- [ ] A typo
- [ ] Missing documentation
- [x] Update Documentation

**Description of the improvement / report**
Current Allure documentation for scalatest is outdated : https://docs.qameta.io/allure/#_scalatest
An updated example for allure scalatest would also be helpful: https://github.com/allure-examples/allure-scalatest-example

Compare the current ScalaTest documentation at docs.qameta.io/allure/#_scalatest with the allure-scalatest-example repository linked in the issue. Identify the outdated guidance and example details, then update the documentation and example so they match; done means the ScalaTest page and linked example are current and consistent.

Written by the indexing model from the issue text.