docs: remove third-party document (#134)

移除三方安装指南，目前已经不适用于 Halo 2.0

/kind documentation

Fixes https://github.com/halo-dev/docs/issues/131

```release-note
None
```

sidebars.js

@@ -39,7 +39,6 @@ module.exports = {
               label: "其他指南",
               items: ["getting-started/install/other/oneinstack"],
             },
-            "getting-started/install/third-party",
           ],
         },
         "getting-started/migrate-from-1.x",