Bump log4js from 6.3.0 to 6.4.0 in /extras/basic_example (#1794)

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: direct:production
...

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extras/basic_example/package.json

@@ -9,7 +9,7 @@
     "body-parser": "~1.19.0",
     "errorhandler": "~1.5.1",
     "express": "~4.17.1",
-    "log4js": "^6.3.0",
+    "log4js": "^6.4.0",
     "morgan": "~1.9.1"
   },
   "contributors": [