Sync content of both "Contributing" pages

This updates the links in `specification/contributing.mdx` to point to
the new repo name, and changes `development/contributing.mdx` to mirror
`specification/contributing.mdx`.  Both files are kept because if the
"User Guide" tab and the "Specification" tab both link to the same file,
then Mintlify gets confused and always switches to the first tab when
navigating to that file.

Author: jonathanhefner

docs/development/contributing.mdx

@@ -3,8 +3,8 @@ title: Contributing
 description: How to participate in Model Context Protocol development
 ---
 
-We welcome contributions from the community! Please review our [contributing guidelines](https://github.com/modelcontextprotocol/.github/blob/main/CONTRIBUTING.md) for details on how to submit changes.
+We welcome contributions from the community! Please review our [contributing guidelines](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/CONTRIBUTING.md) for details on how to submit changes.
 
-All contributors must adhere to our [Code of Conduct](https://github.com/modelcontextprotocol/.github/blob/main/CODE_OF_CONDUCT.md).
+All contributors must adhere to our [Code of Conduct](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/CODE_OF_CONDUCT.md).
 
-For questions and discussions, please use [GitHub Discussions](https://github.com/orgs/modelcontextprotocol/discussions).
+For questions and discussions, please use [GitHub Discussions](https://github.com/modelcontextprotocol/modelcontextprotocol/discussions).

docs/specification/contributing.mdx

@@ -1,17 +1,10 @@
 ---
-title: "Contributions"
-weight: 20
-cascade:
-  type: docs
-breadcrumbs: false
+title: Contributing
+description: How to participate in Model Context Protocol development
 ---
 
-We welcome contributions from the community! Please review our
-[contributing guidelines](https://github.com/modelcontextprotocol/specification/blob/main/CONTRIBUTING.md)
-for details on how to submit changes.
+We welcome contributions from the community! Please review our [contributing guidelines](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/CONTRIBUTING.md) for details on how to submit changes.
 
-All contributors must adhere to our
-[Code of Conduct](https://github.com/modelcontextprotocol/specification/blob/main/CODE_OF_CONDUCT.md).
+All contributors must adhere to our [Code of Conduct](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/CODE_OF_CONDUCT.md).
 
-For questions and discussions, please use
-[GitHub Discussions](https://github.com/modelcontextprotocol/specification/discussions).
+For questions and discussions, please use [GitHub Discussions](https://github.com/modelcontextprotocol/modelcontextprotocol/discussions).