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

@@ -684,19 +684,6 @@
         "url": "https://github.com/semgrep/mcp-marketplace.git"
       },
       "homepage": "https://github.com/semgrep/mcp-marketplace.git"
-    },
-    {
-      "name": "railway",
-      "description": "Deploy and manage apps, databases, and infrastructure on Railway. Covers project setup, deploys, environment configuration, networking, troubleshooting, and monitoring.",
-      "category": "deployment",
-      "source": {
-        "source": "git-subdir",
-        "url": "railwayapp/railway-skills",
-        "path": "plugins/railway",
-        "ref": "main",
-        "sha": "d52f3741a6a33a3191d6138eb3d6c3355cb970d1"
-      },
-      "homepage": "https://docs.railway.com/ai/claude-code-plugin"
     }
   ]
 }