Trim the Actions comparison to actual differences (#638)

`$/` is [GitHub's self-repository prefix](https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#example-using-an-action-in-the-same-repository-as-the-workflow-at-the-running-commit-recommended) with the same semantics, so it is no Gitea addition. The `builtin:checkout` input list was outdated since https://gitea.com/gitea/runner/pulls/1277 made it match `actions/checkout`.

Reviewed-on: https://gitea.com/gitea/docs/pulls/638
Reviewed-by: Lunny Xiao <[email protected]>
Co-authored-by: silverwind <[email protected]>

i18n/zh-cn/docs/version-28/usage/actions/comparison.md

@@ -21,15 +21,7 @@ Gitea Actions旨在与GitHub Actions兼容，差异如下。
 `uses:`支持以下前缀：
 
 - `self:`引用您自己的Gitea实例，例如`uses: self:owner/repo@v1`或`uses: self:owner/repo/.gitea/workflows/build.yml@v1`
-- `builtin:`运行Gitea Runner内置的Action，无需下载，Job镜像中也无需Node，例如`uses: builtin:checkout`
-
-`builtin:checkout`支持`actions/checkout`的`repository`、`ref`、`token`、`path`和`fetch-depth`输入，默认值相同，其他输入会使步骤失败。
-
-<a id="workflow-relative-actions"></a>
-### 相对于工作流的Actions
-
-`$/`引用工作流所在的仓库和提交，或外层复合Action所在的仓库和提交，例如`uses: $/.gitea/actions/build`。
-与`./`不同，它无需事先检出代码。
+- `builtin:`运行Gitea Runner内置的Action，无需下载，也不依赖Node.js，例如`uses: builtin:checkout`
 
 ### 使用Go编写Actions
 
@@ -95,7 +87,7 @@ Gitea Actions旨在与GitHub Actions兼容，差异如下。
 
 未指定主机的Actions（如`uses: actions/checkout@v4`）会从`https://github.com`下载，当`[actions].DEFAULT_ACTIONS_URL`为`self`时则从您自己的实例下载。
 请参阅[配置备忘单](../../administration/config-cheat-sheet.md#actions-actions)。
-其他来源请参阅[Action URL绝对路径](#absolute-action-urls)、[Action前缀](#action-prefixes)和[相对于工作流的Actions](#workflow-relative-actions)。
+其他来源请参阅[Action URL绝对路径](#absolute-action-urls)和[Action前缀](#action-prefixes)。
 
 ### 上下文可用性