fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-6152404
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-6152404
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-6160000
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-6160000

Dockerfile

@@ -4,7 +4,7 @@
 
 # build nginx with only the bare minimum of features or modules
 # Note: no need to chain the RUN commands here as it's a builder image and nothing will be kept
-FROM alpine:3.18 as nginx-builder
+FROM alpine:3 as nginx-builder
 
 ENV NGINX_VERSION=1.24.0
 # pin nginx modules versions
@@ -111,7 +111,7 @@ USER root
 RUN make install
 
 # CRONIE BUILDER
-FROM alpine:3.18 as cronie-builder
+FROM alpine:3 as cronie-builder
 ENV CRONIE_VERSION=1.5.7
 # install dependencies
 RUN apk add --no-cache build-base libc-dev make gcc autoconf automake abuild musl-obstack-dev
@@ -132,7 +132,7 @@ RUN abuild-keygen -n -a && abuild && find /home/builder/packages -type f -name '
 #############################
 # ELABFTW + NGINX + PHP-FPM #
 #############################
-FROM alpine:3.18
+FROM alpine:3
 
 # this is versioning for the container image
 ENV ELABIMG_VERSION=5.0.0