fix(docs): make integrations.json strict-valid (drop trailing comma)

The last entry had a trailing comma, so build-docs' 'Check integrations'
step (strict JSON.parse) failed on main and every PR. Drop it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: DK09876

hindsight-docs/src/data/integrations.json

@@ -519,6 +519,6 @@
       "category": "tool",
       "link": "https://github.com/yugandhar-maram/agrasandhany",
       "icon": "/img/icons/obsidian.svg"
-    },
+    }
   ]
 }