chore(deps-dev): bump mysql2

Bumps [mysql2](https://github.com/sidorares/node-mysql2) from 2.3.0 to 3.9.4.
- [Release notes](https://github.com/sidorares/node-mysql2/releases)
- [Changelog](https://github.com/sidorares/node-mysql2/blob/master/Changelog.md)
- [Commits](sidorares/node-mysql2@v2.3.0...v3.9.4)

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

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

plugins/node/opentelemetry-instrumentation-mysql2/package.json

@@ -57,7 +57,7 @@
     "@types/semver": "7.3.8",
     "gts": "3.1.0",
     "mocha": "7.2.0",
-    "mysql2": "2.3.0",
+    "mysql2": "3.9.4",
     "nyc": "15.1.0",
     "rimraf": "3.0.2",
     "semver": "7.3.5",