Bump apache-airflow from 2.1.0 to 2.1.2 in /similar-users

Bumps [apache-airflow](https://github.com/apache/airflow) from 2.1.0 to 2.1.2.
- [Release notes](https://github.com/apache/airflow/releases)
- [Changelog](https://github.com/apache/airflow/blob/main/CHANGELOG.txt)
- [Commits](https://github.com/apache/airflow/compare/2.1.0...2.1.2

)

---
updated-dependencies:
- dependency-name: apache-airflow
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

similar-users/requirements.txt

-apache-airflow==2.1.0
+apache-airflow==2.1.2
 apache-airflow-providers-papermill==1.0.2
 jupyter==1.0.0
 pytest-flask==1.1.0