Bumps alpine from 3.13.3 to 3.13.4. Signed-off-by: dependabot[bot] <support@github.com>
@@ -1,4 +1,4 @@
-FROM alpine:3.13.3
+FROM alpine:3.13.4
ARG DOVECOT_PACKAGE_VERSION=2.3.13-r0
ARG SOCAT_PACKAGE_VERSION=1.7.4.1-r0