Fix some incorrect links in docs (#28191) (#28201)

Backport #28191 by @yp05327


https://gitea.com/gitea/gitea-docusaurus/actions/runs/661/jobs/0#jobstep-9-39
I noticed that there are many warning logs in building docs.
It is causing 404 in docs.gitea.com now, so we need to fix it.
And there are also some other problems in v1.19 which can not be done in
this PR.

Co-authored-by: yp05327 <576951401@qq.com>

docs/content/help/faq.en-us.md

@@ -39,7 +39,6 @@ If a bug fix is targeted on 1.20.1 but 1.20.1 is not released yet, you can get t
 
 To migrate from Gogs to Gitea:
 
-- [Gogs version 0.9.146 or less](installation/upgrade-from-gogs.md)
 - [Gogs version 0.11.46.0418](https://github.com/go-gitea/gitea/issues/4286)
 
 To migrate from GitHub to Gitea, you can use Gitea's built-in migration form.

docs/content/help/faq.zh-cn.md

@@ -41,7 +41,6 @@ menu:
 
 要从Gogs迁移到Gitea：
 
-- [Gogs版本0.9.146或更低](installation/upgrade-from-gogs.md)
 - [Gogs版本0.11.46.0418](https://github.com/go-gitea/gitea/issues/4286)
 
 要从GitHub迁移到Gitea，您可以使用Gitea内置的迁移表单。