chore(deps): update alpine docker tag to v3.20.0 (#16)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| alpine | final | minor | `3.18.4` -> `3.20.0` |

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### Configuration

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Co-authored-by: OCram85 <marco.blessing@googlemail.com>
Reviewed-on: https://gitea.ocram85.com/OCram85/swarmproxy/pulls/16
Reviewed-by: OCram85 <marco.blessing@googlemail.com>
Co-authored-by: renovate-bot <renovate@ocram85.com>
Co-committed-by: renovate-bot <renovate@ocram85.com>

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.18.4
+FROM alpine:3.20.0
 
 # Set labels manually, each build service differs in used or predefined labels.
 LABEL maintainer="OCram85"