Update index.md to use https as git clone url for better security

doc/user/project/deploy_tokens/index.md

@@ -65,7 +65,7 @@ To download a repository using a Deploy Token, you just need to:
 1. `git clone` the project using the Deploy Token:
 
    ```shell
-   git clone http://<username>:<deploy_token>@gitlab.example.com/tanuki/awesome_project.git
+   git clone https://<username>:<deploy_token>@gitlab.example.com/tanuki/awesome_project.git
    ```
 
 Replace `<username>` and `<deploy_token>` with the proper values.