Dockerfile: fix alpine version

The go1.20 image is not published with alpine 3.15; updating the version.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Dockerfile

@@ -1,5 +1,5 @@
 ARG BASE_IMAGE_BUILDER=golang
-ARG ALPINE_VERSION=3.15
+ARG ALPINE_VERSION=3.19
 ARG GO_VERSION=1.20
 
 FROM ${BASE_IMAGE_BUILDER}:${GO_VERSION}-alpine${ALPINE_VERSION} AS builder