⬆️ Bump alpine from 3.18.2 to 3.18.3 (#67)

Bumps alpine from 3.18.2 to 3.18.3.

---
updated-dependencies:
- dependency-name: alpine
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.18.2 as builder
+FROM alpine:3.18.3 as builder
 
 WORKDIR /go/src/github.com/systemli/prometheus-etherpad-exporter