Update alpine Docker tag to v3.20.3

Author: renovate[bot]

backend/deployment/backend/Dockerfile

@@ -26,7 +26,7 @@ COPY pkg pkg
 RUN go install -ldflags="-X main.gitRef=${SOURCE_BRANCH} -X main.gitHash=${SOURCE_COMMIT}" ./cmd/backend
 
 ###############################################################
-FROM alpine:3.19.1@sha256:c5b1261d6d3e43071626931fc004f70149baeba2c8ec672bd4f27761f8e1ad6b
+FROM alpine:3.20.3@sha256:beefdbd8a1da6d2915566fde36db9db0b524eb737fc57cd1367effd16dc0d06d
 
 ENV JAEGER_SERVICE_NAME Dinghy
 ENV JAEGER_SAMPLER_TYPE const

notify/deployment/notify/Dockerfile

@@ -30,7 +30,7 @@ COPY pkg pkg
 RUN go install -ldflags="-X main.gitRef=${SOURCE_BRANCH} -X main.gitHash=${SOURCE_COMMIT}" ./cmd/notify
 
 ###############################################################
-FROM alpine:3.19.1@sha256:c5b1261d6d3e43071626931fc004f70149baeba2c8ec672bd4f27761f8e1ad6b
+FROM alpine:3.20.3@sha256:beefdbd8a1da6d2915566fde36db9db0b524eb737fc57cd1367effd16dc0d06d
 
 ENV JAEGER_SERVICE_NAME Dinghy-Notify
 ENV JAEGER_SAMPLER_TYPE const