Bump mysql2 from 2.1.0 to 3.22.0 in /react-express-mysql/backend

Bumps [mysql2](https://github.com/sidorares/node-mysql2) from 2.1.0 to 3.22.0.
- [Release notes](https://github.com/sidorares/node-mysql2/releases)
- [Changelog](https://github.com/sidorares/node-mysql2/blob/master/Changelog.md)
- [Commits](https://github.com/sidorares/node-mysql2/compare/v2.1.0...v3.22.0)

---
updated-dependencies:
- dependency-name: mysql2
  dependency-version: 3.22.0
  dependency-type: direct:production
...

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

react-express-mysql/backend/package.json

@@ -17,7 +17,7 @@
     "express": "^4.17.1",
     "knex": "^0.95.11",
     "morgan": "^1.10.0",
-    "mysql2": "^2.1.0"
+    "mysql2": "^3.22.0"
   },
   "devDependencies": {
     "chai": "^4.2.0",