Update alpine:latest Docker digest to 51b6726

Dockerfile

@@ -15,7 +15,7 @@ COPY *.go ./
 RUN go build -o webex-notifier
 
 # final stage
-FROM alpine:latest@sha256:34871e7290500828b39e22294660bee86d966bc0017544e848dd9a255cdf59e0
+FROM alpine:latest@sha256:51b67269f354137895d43f3b3d810bfacd3945438e94dc5ac55fdac340352f48
 COPY --from=build-env /go/src/webex-notifier/webex-notifier  /usr/local/bin/webex-notifier
 RUN mkdir -p /output
 ENV DIRECTORY /output