Update alpine:latest Docker digest to a8560b3 (#120)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Dockerfile

@@ -15,7 +15,7 @@ COPY *.go ./
 RUN go build -o confluence-gardner
 
 # final stage
-FROM alpine:latest@sha256:56fa17d2a7e7f168a043a2712e63aed1f8543aeafdcee47c58dcffe38ed51099
+FROM alpine:latest@sha256:a8560b36e8b8210634f77d9f7f9efd7ffa463e380b75e2e74aff4511df3ef88c
 COPY --from=build-env /go/src/confluence-gardner/confluence-gardner  /usr/local/bin/confluence-gardner
 RUN mkdir -p /output
 ENV DIRECTORY /output