Remove the original signals.yml prototype and supporting code (#373)

This style of manually tracking signals is no longer in the cards. In
particular, for surveys, we now have this annotated directly in some
surveys and extracted automatically. Example here:
https://web-platform-dx.github.io/web-features-explorer/features/customizable-select/

Author: foolip

index.ts

@@ -8,27 +8,21 @@
     "url": "https://github.com/web-platform-dx/developer-signals.git"
   },
   "type": "module",
-  "main": "index.ts",
   "engines": {
     "node": ">=18.19.0"
   },
   "scripts": {
-    "test": "npm run test:schema && npm run test:format",
-    "test:schema": "tsx scripts/schema.ts",
+    "test": "npm run test:format",
     "test:format": "prettier --check .",
     "format": "npx prettier --write .",
     "update-issues": "tsx scripts/update-issues.ts"
   },
   "devDependencies": {
     "@octokit/plugin-throttling": "^11.0.1",
     "@octokit/rest": "^22.0.0",
-    "@types/node": "^18.19.18",
-    "ajv": "^8.12.0",
-    "ajv-formats": "^2.1.1",
     "prettier": "^3.2.5",
     "tsx": "^4.7.1",
     "typescript": "^5.3.3",
-    "web-features": "^2.45.0",
-    "yaml": "^2.4.0"
+    "web-features": "^2.45.0"
   }
 }