docs: Fix missing comma in MCP code snippet (#32126)

the docs now contain valid json

Closes #ISSUE

Release Notes:

- N/A *or* Added/Fixed/Improved ...

docs/src/ai/mcp.md

@@ -36,7 +36,7 @@ Alternatively, you can connect to MCP servers in Zed via adding their commands d
         "path": "some-command",
         "args": ["arg-1", "arg-2"],
         "env": {}
-      }
+      },
       "settings": {}
     }
   }