Bump mysql2 from 3.6.1 to 3.9.7 (#20)

Bumps [mysql2](https://github.com/sidorares/node-mysql2) from 3.6.1 to 3.9.7.
- [Release notes](https://github.com/sidorares/node-mysql2/releases)
- [Changelog](https://github.com/sidorares/node-mysql2/blob/master/Changelog.md)
- [Commits](sidorares/node-mysql2@v3.6.1...v3.9.7)

---
updated-dependencies:
- dependency-name: mysql2
  dependency-type: direct:production
...

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Author: dependabot[bot]