Bump select2 from 4.0.3 to 4.0.6 in /public/backend/pengurus

Bumps [select2](https://github.com/select2/select2) from 4.0.3 to 4.0.6.
- [Release notes](https://github.com/select2/select2/releases)
- [Changelog](https://github.com/select2/select2/blob/develop/CHANGELOG.md)
- [Commits](select2/select2@4.0.3...4.0.6)

---
updated-dependencies:
- dependency-name: select2
  dependency-type: direct:production
...

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

public/backend/pengurus/package.json

@@ -55,7 +55,7 @@
     "morris.js": "^0.5.0",
     "pace": "0.0.4",
     "raphael": "^2.2.7",
-    "select2": "^4.0.3",
+    "select2": "^4.0.6",
     "slimscroll": "^0.9.1"
   }
 }