Update debian:stable-slim Docker digest to a771c85

Author: renovate[bot]

build/Dockerfile

@@ -15,7 +15,7 @@ FROM busybox AS busybox
 RUN addgroup -S pulsegroup && adduser -S -G pulsegroup pulseuser
 
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-FROM debian:stable-slim@sha256:50db38a20a279ccf50761943c36f9e82378f92ef512293e1239b26bb77a8b496 AS certs
+FROM debian:stable-slim@sha256:a771c85b2287eae7ce8fe0a4c2637d575c5d991555ae680c187c5572153648d9 AS certs
 RUN apt-get update && apt-get install -y ca-certificates
 
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