Update webhook closed PR message link to clau.de

Replace the Google Forms link with the new plugin directory
submission link (https://clau.de/plugin-directory-submission).

https://claude.ai/code/session_01NxRDJKDvFR2d4wC4ppDEDT

.claude-plugin/marketplace.json

@@ -684,20 +684,6 @@
         "url": "https://github.com/semgrep/mcp-marketplace.git"
       },
       "homepage": "https://github.com/semgrep/mcp-marketplace.git"
-    },
-    {
-      "name": "sanity-plugin",
-      "description": "Sanity content platform integration with MCP server, agent skills, and slash commands. Query and author content, build and optimize GROQ queries, design schemas, and set up Visual Editing.",
-      "category": "development",
-      "author": {
-        "name": "Sanity"
-      },
-      "source": {
-        "source": "url",
-        "url": "https://github.com/sanity-io/agent-toolkit.git",
-        "sha": "4b1fb10bd707a22cf0cdfad5374ffc885f2ffa8d"
-      },
-      "homepage": "https://www.sanity.io"
     }
   ]
 }