Pin dependency @types/google-protobuf to 3.15.6 (#32)

Co-authored-by: Renovate Bot <[email protected]>

Author: renovate[bot]

bindings/typescript/package.json

@@ -11,7 +11,7 @@
     "google-protobuf": "^3.20.1"
   },
   "devDependencies": {
-    "@types/google-protobuf": "^3.15.6",
+    "@types/google-protobuf": "3.15.6",
     "protoc-gen-ts": "0.8.1",
     "typescript": "^4.6.4"
   },