fix: Update @langchain/core to resolve missing export 'convertToProviderContentBlock' error

[magicianA]

this fixes #355
@bracesproul

[vercel]

@magicianA is attempting to deploy a commit to the LangChain Team on Vercel.

A member of the Team first needs to authorize it.

[iqdoctor]

I just add

  "resolutions": {
    "@langchain/core": "0.3.68",
    "@langchain/openai": "0.5.11",
    "langchain": "0.3.27",
    "@langchain/langgraph": "0.2.73",
    "prosemirror-view": "1.37.2"
  }

to package.json

[jacoblee93]

Hey just fixed this in another PR - thanks for opening.