Bump mako from 1.3.6 to 1.3.12 in /.generator

Bumps [mako](https://github.com/sqlalchemy/mako) from 1.3.6 to 1.3.12.
- [Release notes](https://github.com/sqlalchemy/mako/releases)
- [Changelog](https://github.com/sqlalchemy/mako/blob/main/CHANGES)
- [Commits](https://github.com/sqlalchemy/mako/commits)

---
updated-dependencies:
- dependency-name: mako
  dependency-version: 1.3.12
  dependency-type: indirect
...

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