Bump alpine from 3.16.2 to 3.16.3 (#33)

Dockerfile

@@ -1,4 +1,4 @@
-FROM docker.io/alpine:3.16.2
+FROM docker.io/alpine:3.16.3
 
 ARG BORGBACKUP_PACKAGE_VERSION=1.2.0-r0
 ARG OPENSSH_SERVER_PACKAGE_VERSION=9.0_p1-r2