deps: Update alpine:3 Docker digest to 8a1f59f (GoogleCloudPlatform#2454)

Author: renovate-bot

Dockerfile.alpine

@@ -26,7 +26,7 @@ RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} \
     go build -ldflags "-X github.com/GoogleCloudPlatform/cloud-sql-proxy/v2/cmd.metadataString=container.alpine"
 
 # Final stage
-FROM alpine:3@sha256:a8560b36e8b8210634f77d9f7f9efd7ffa463e380b75e2e74aff4511df3ef88c
+FROM alpine:3@sha256:8a1f59ffb675680d47db6337b49d22281a139e9d709335b492be023728e11715
 
 LABEL org.opencontainers.image.source="https://github.com/GoogleCloudPlatform/cloud-sql-proxy"