chore(mcp): drop the changeset already consumed by v7.40.0

#881 was squash-merged and released, so sampo turned
mcp-sdk-v2-support.md into the 7.40.0 changelog entry and deleted it from
main. This branch predates that merge and still carried the file; because
the squash gave main no shared history with the branch, git saw "main never
had this file" rather than a modify/delete and silently kept it — which
would have re-emitted the entire v7.40.0 entry in the next release.

Generated-By: PostHog Code
Task-Id: ebafcb71-b03b-443d-b40c-d527ed4a04f4

Author: gesh