Bump http-cache-semantics and npm in /samples/js-workbench-customizer

Removes [http-cache-semantics](https://github.com/kornelski/http-cache-semantics). It's no longer used after updating ancestor dependency [npm](https://github.com/npm/cli). These dependencies need to be updated together.


Removes `http-cache-semantics`

Updates `npm` from 6.7.0 to 9.4.1
- [Release notes](https://github.com/npm/cli/releases)
- [Changelog](https://github.com/npm/cli/blob/latest/CHANGELOG.md)
- [Commits](https://github.com/npm/cli/compare/v6.7.0...v9.4.1)

---
updated-dependencies:
- dependency-name: http-cache-semantics
  dependency-type: indirect
- dependency-name: npm
  dependency-type: direct:production
...

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

samples/js-workbench-customizer/package.json

@@ -19,7 +19,7 @@
     "@microsoft/sp-webpart-base": "1.10.0",
     "@types/es6-promise": "0.0.33",
     "@types/webpack-env": "1.13.1",
-    "npm": "^6.7.0"
+    "npm": "^9.4.1"
   },
   "devDependencies": {
     "@microsoft/rush-stack-compiler-3.3": "0.3.5",