Drop unused dependency (#123)

Author: Kludex

gateway/package.json

@@ -13,7 +13,6 @@
     "@opentelemetry/resources": "^2.0.1",
     "@pydantic/genai-prices": "^0.0.35",
     "@pydantic/logfire-api": "^0.9.0",
-    "@streamparser/json-whatwg": "^0.0.22",
     "eventsource-parser": "^3.0.6",
     "mime-types": "^3.0.1",
     "ts-pattern": "^5.8.0"