Bump alpine from 3.18.0 to 3.18.2 (#56)

Dockerfile

@@ -1,4 +1,4 @@
-FROM docker.io/alpine:3.18.0
+FROM docker.io/alpine:3.18.2
 
 ARG DOVECOT_PACKAGE_VERSION=2.3.20-r10
 ARG SOCAT_PACKAGE_VERSION=1.7.4.4-r1