Bump alpine from 3.19.1 to 3.20.0

Bumps alpine from 3.19.1 to 3.20.0.

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

Signed-off-by: dependabot[bot] <support@github.com>

Dockerfile

@@ -4,7 +4,7 @@ WORKDIR /go/src/github.com/mackerelio/mkr/
 COPY . .
 RUN make build
 
-FROM alpine:3.19.1
+FROM alpine:3.20.0
 RUN apk add --no-cache ca-certificates
 COPY --from=builder /go/src/github.com/mackerelio/mkr/mkr /usr/local/bin/
 ENTRYPOINT ["/usr/local/bin/mkr"]