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

@@ -684,18 +684,6 @@
         "url": "https://github.com/semgrep/mcp-marketplace.git"
       },
       "homepage": "https://github.com/semgrep/mcp-marketplace.git"
-    },
-    {
-      "name": "migration-to-aws",
-      "description": "Assess current cloud provider usage and billing to estimate and compare AWS services and pricing, with recommendations for migration or continued use of current provider.",
-      "category": "migration",
-      "source": {
-        "source": "git-subdir",
-        "url": "https://github.com/awslabs/agent-plugins.git",
-        "path": "plugins/migration-to-aws",
-        "ref": "main"
-      },
-      "homepage": "https://github.com/awslabs/agent-plugins"
     }
   ]
 }