Update ghcr.io/tecnativa/docker-socket-proxy Docker tag to v0.4.0 (#1326)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [ghcr.io/tecnativa/docker-socket-proxy](https://github.com/Tecnativa/docker-socket-proxy) | minor | `0.3.0` -> `v0.4.0` |

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### Release Notes

<details>
<summary>Tecnativa/docker-socket-proxy (ghcr.io/tecnativa/docker-socket-proxy)</summary>

### [`v0.4.0`](https://github.com/Tecnativa/docker-socket-proxy/releases/tag/v0.4.0)

[Compare Source](Tecnativa/docker-socket-proxy@v0.3.0...v0.4.0)

#### What's Changed

- test: check if connection upgrades work (using exec) by [@&#8203;proudier](https://github.com/proudier) in Tecnativa/docker-socket-proxy#139
- \[ADD] v1.51 version to README.md and Modernice CI by [@&#8203;josep-tecnativa](https://github.com/josep-tecnativa) in Tecnativa/docker-socket-proxy#152
- Updated the underlying haproxy version from 2.2 to 3.2.4 by [@&#8203;Programmer-Admin](https://github.com/Programmer-Admin) in Tecnativa/docker-socket-proxy#156

#### New Contributors

- [@&#8203;Programmer-Admin](https://github.com/Programmer-Admin) made their first contribution in Tecnativa/docker-socket-proxy#156

**Full Changelog**: Tecnativa/docker-socket-proxy@v0.3.0...v0.4.0

</details>

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Reviewed-on: https://gitea.alexlebens.dev/alexlebens/infrastructure/pulls/1326
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Author: Renovate Bot

hosts/ps10rp/homepage/compose.yaml

@@ -20,7 +20,7 @@ services:
             - /dev/net/tun:/dev/net/tun
 
     dockerproxy:
-        image: ghcr.io/tecnativa/docker-socket-proxy:0.3.0
+        image: ghcr.io/tecnativa/docker-socket-proxy:v0.4.0
         container_name: homepage-dockerproxy
         environment:
             - CONTAINERS=1