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

@@ -684,17 +684,6 @@
         "url": "https://github.com/semgrep/mcp-marketplace.git"
       },
       "homepage": "https://github.com/semgrep/mcp-marketplace.git"
-    },
-    {
-      "name": "mintlify",
-      "description": "Build beautiful documentation sites with Mintlify. Convert non-markdown files into properly formatted MDX pages, add and modify content with correct component use, and automate documentation updates.",
-      "category": "development",
-      "source": {
-        "source": "url",
-        "url": "https://github.com/mintlify/mintlify-claude-plugin.git",
-        "sha": "ce435be18a700dc849d6a63a80da4816d1e2128c"
-      },
-      "homepage": "https://www.mintlify.com/"
     }
   ]
 }