Bump mcp from 0.3.0 to 0.4.0 (#3)

Bumps [mcp](https://github.com/modelcontextprotocol/ruby-sdk) from 0.3.0 to 0.4.0.
- [Release notes](https://github.com/modelcontextprotocol/ruby-sdk/releases)
- [Changelog](https://github.com/modelcontextprotocol/ruby-sdk/blob/main/CHANGELOG.md)
- [Commits](modelcontextprotocol/ruby-sdk@v0.3.0...v0.4.0)

---
updated-dependencies:
- dependency-name: mcp
  dependency-version: 0.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -138,7 +138,7 @@ GEM
       net-pop
       net-smtp
     marcel (1.1.0)
-    mcp (0.3.0)
+    mcp (0.4.0)
       json-schema (>= 4.1)
       json_rpc_handler (~> 0.1)
     mini_mime (1.1.5)