Update actions variables documents (#30394)

Fix #30393

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Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Zettat123 <zettat123@gmail.com>

docs/content/usage/actions/act-runner.en-us.md

@@ -303,34 +303,3 @@ sudo systemctl enable act_runner --now
 ```
 
 If using Docker, the `act_runner` user should also be added to the `docker` group before starting the service. Keep in mind that this effectively gives `act_runner` root access to the system [[1]](https://docs.docker.com/engine/security/#docker-daemon-attack-surface).
-
-## Configuration variable
-
-You can create configuration variables on the user, organization and repository level.
-The level of the variable depends on where you created it.
-
-### Naming conventions
-
-The following rules apply to variable names:
-
-- Variable names can only contain alphanumeric characters (`[a-z]`, `[A-Z]`, `[0-9]`) or underscores (`_`). Spaces are not allowed.
-
-- Variable names must not start with the `GITHUB_` and `GITEA_` prefix.
-
-- Variable names must not start with a number.
-
-- Variable names are case-insensitive.
-
-- Variable names must be unique at the level they are created at.
-
-- Variable names must not be `CI`.
-
-### Using variable
-
-After creating configuration variables, they will be automatically filled in the `vars` context.
-They can be accessed through expressions like `{{ vars.VARIABLE_NAME }}` in the workflow.
-
-### Precedence
-
-If a variable with the same name exists at multiple levels, the variable at the lowest level takes precedence:
-A repository variable will always be chosen over an organization/user variable.