Bump sqlalchemy from 1.2.14 to 1.2.15 in /{{cookiecutter.app_name}}

Bumps [sqlalchemy](https://github.com/sqlalchemy/sqlalchemy) from 1.2.14 to 1.2.15.
- [Release notes](https://github.com/sqlalchemy/sqlalchemy/releases)
- [Changelog](https://github.com/sqlalchemy/sqlalchemy/blob/master/CHANGES)
- [Commits](https://github.com/sqlalchemy/sqlalchemy/commits

)

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