Bump log4js from 6.3.0 to 6.4.0

Bumps [log4js](https://github.com/log4js-node/log4js-node) from 6.3.0 to 6.4.0.
- [Release notes](https://github.com/log4js-node/log4js-node/releases)
- [Changelog](https://github.com/log4js-node/log4js-node/blob/master/CHANGELOG.md)
- [Commits](log4js-node/log4js-node@v6.3.0...v6.4.0)

---
updated-dependencies:
- dependency-name: log4js
  dependency-type: indirect
...

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