Fix URL In Gitea Actions Badge Docs (#31191) (#31198)

Backport #31191 by @TheBrokenRail

The example URL given in the documentation leads to a 404.

For instance,
`https://your-gitea-instance.com/{owner}/{repo}/actions/workflows/{workflow_file}?branch={branch}&event={event}`
translates to
`https://gitea.thebrokenrail.com/minecraft-pi-reborn/minecraft-pi-reborn/actions/workflows/build.yml`,
which is a 404.

I had to check the [linked GitHub
docs](https://docs.github.com/en/actions/monitoring-and-troubleshooting-workflows/adding-a-workflow-status-badge)
to learn that you have to add `/badge.svg` to the URL.

Example:
https://gitea.thebrokenrail.com/minecraft-pi-reborn/minecraft-pi-reborn/actions/workflows/build.yml/badge.svg

Co-authored-by: TheBrokenRail <17478432+TheBrokenRail@users.noreply.github.com>

docs/content/usage/actions/badge.en-us.md

@@ -25,7 +25,7 @@ It is designed to be compatible with [GitHub Actions workflow badge](https://doc
 You can use the following URL to get the badge:
 
 ```
-https://your-gitea-instance.com/{owner}/{repo}/actions/workflows/{workflow_file}?branch={branch}&event={event}
+https://your-gitea-instance.com/{owner}/{repo}/actions/workflows/{workflow_file}/badge.svg?branch={branch}&event={event}
 ```
 
 - `{owner}`: The owner of the repository.