Remove scripts/cxx-api (#55162)

Summary:
Pull Request resolved: #55162

Changelog: [Internal]

Removes `scripts/cxx-api`, containing the legacy C++ API tracking code.

Reviewed By: cortinico

Differential Revision: D90675176

fbshipit-source-id: ed920f3e19a302f8451bcc0c2a827c99570d6cb8

Author: j-piasecki

package.json

@@ -11,7 +11,6 @@
     "build-types": "node ./scripts/js-api/build-types",
     "clang-format": "clang-format -i --glob=*/**/*.{h,cpp,m,mm}",
     "clean": "node ./scripts/build/clean.js",
-    "cxx-api-build": "node ./scripts/cxx-api/public-api.js",
     "flow-check": "flow check",
     "flow": "flow",
     "format-check": "prettier --list-different \"./**/*.{js,md,yml,ts,tsx}\"",