fix: remove unused @langchain/community peer dep from sdk-js

@copilotkit/sdk-js declares @langchain/community as a peer dependency
but never imports from it. The ^0.3.58 constraint was the only thing
blocking @langchain/core@1.x resolution for consumers. Remove it
entirely since it serves no purpose.

Author: AlemTuzlak

packages/sdk-js/package.json

@@ -79,7 +79,6 @@
     "vitest": "^3.2.4"
   },
   "peerDependencies": {
-    "@langchain/community": "^0.3.58",
     "@langchain/core": ">=0.4.0 <2.0.0",
     "@langchain/langgraph": ">=0.4.0 <2.0.0",
     "langchain": ">=1.0.0",