Bump alpine from 3.16.2 to 3.16.3 (#25)

Dockerfile

@@ -1,4 +1,4 @@
-FROM docker.io/alpine:3.16.2
+FROM docker.io/alpine:3.16.3
 
 ARG OPENVPN_PACKAGE_VERSION=2.5.6-r1
 RUN apk add --no-cache openvpn=$OPENVPN_PACKAGE_VERSION