Update path related documents (#25417) (#25982)

Backport #25417 by @wxiaoguang

Update WorkPath/WORK_PATH related documents, remove out-dated
information.

Remove "StaticRootPath" on the admin config display page, because few
end user really need it, it only causes misconfiguration.


![image](8095afa4-da76-436b-9e89-2a92c229c01d)

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

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

@@ -59,11 +59,12 @@ https://github.com/loganinak/MigrateGitlabToGogs
 ## Where does Gitea store what file
 
 - _`AppWorkPath`_
-  - The `--work-path` flag
+  - The `WORK_PATH` option in `app.ini`
+  - Else the `--work-path` flag
   - Else Environment variable `GITEA_WORK_DIR`
   - Else a built-in value set at build time
   - Else the directory that contains the Gitea binary
-- `%(APP_DATA_PATH)` (default for database, indexers, etc.)
+- `AppDataPath` (default for database, indexers, etc.)
   - `APP_DATA_PATH` from `app.ini`
   - Else _`AppWorkPath`_`/data`
 - _`CustomPath`_ (custom templates)
@@ -112,9 +113,6 @@ Gitea's custom templates must be added to the correct location or Gitea will not
 The correct path for the template(s) will be relative to the `CustomPath`
 
 1. To find `CustomPath`, look for Custom File Root Path in Site Administration -> Configuration
-
-    If that doesn't exist, you can try `echo $GITEA_CUSTOM`
-
 2. If you are still unable to find a path, the default can be [calculated above](#where-does-gitea-store-what-file)
 3. Once you have figured out the correct custom path, you can refer to the [customizing Gitea]({{< relref "doc/administration/customizing-gitea.en-us.md" >}}) page to add your template to the correct location.