Bump the babylon group in /visualiser with 2 updates

Bumps the babylon group in /visualiser with 2 updates: [@babylonjs/core](https://github.com/BabylonJS/Babylon.js) and [@babylonjs/gui](https://github.com/BabylonJS/Babylon.js).


Updates `@babylonjs/core` from 6.18.0 to 6.20.1
- [Release notes](https://github.com/BabylonJS/Babylon.js/releases)
- [Changelog](https://github.com/BabylonJS/Babylon.js/blob/master/CHANGELOG.md)
- [Commits](BabylonJS/Babylon.js@6.18.0...6.20.1)

Updates `@babylonjs/gui` from 6.18.0 to 6.20.1
- [Release notes](https://github.com/BabylonJS/Babylon.js/releases)
- [Changelog](https://github.com/BabylonJS/Babylon.js/blob/master/CHANGELOG.md)
- [Commits](BabylonJS/Babylon.js@6.18.0...6.20.1)

---
updated-dependencies:
- dependency-name: "@babylonjs/core"
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: babylon
- dependency-name: "@babylonjs/gui"
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: babylon
...

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

visualiser/package.json

@@ -1,7 +1,7 @@
 {
   "dependencies": {
-    "@babylonjs/core": "^6.18.0",
-    "@babylonjs/gui": "^6.18.0"
+    "@babylonjs/core": "^6.20.1",
+    "@babylonjs/gui": "^6.20.1"
   },
   "devDependencies": {
     "ts-loader": "^9.4.4",