Remove cpx from package.json in twenty-ui since it was unused and caused dependabot alert. (#15147)

Fixes [Dependabot Alert
102](https://github.com/twentyhq/twenty/security/dependabot/102) -
uncontrolled resource consumption in braces.

braces@1.8.5 was coming from the cpx@1.5.0 dependency in
packages/twenty-ui/package.json. That release of cpx dragged in
chokidar@1.7.0 → micromatch@2.3.11 → braces@^1.8.2.

Now, even though there are mentions of `braces: "npm:~3.0.2"` in
yarn.lock, it resolves to `3.0.3` since ~ allows latest patch in semver.

packages/twenty-ui/package.json

@@ -16,7 +16,6 @@
     "babel-plugin-inline-import": "^3.0.0",
     "babel-plugin-inline-react-svg": "^2.0.2",
     "babel-plugin-module-resolver": "^5.0.2",
-    "cpx": "^1.5.0",
     "tsx": "^4.19.3",
     "vite-plugin-svgr": "^4.3.0"
   },