fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE319-BUSYBOX-6913413
- https://snyk.io/vuln/SNYK-ALPINE319-BUSYBOX-6928845
- https://snyk.io/vuln/SNYK-ALPINE319-BUSYBOX-6928846
- https://snyk.io/vuln/SNYK-ALPINE319-BUSYBOX-6928846
- https://snyk.io/vuln/SNYK-ALPINE319-BUSYBOX-6928847

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.19 as builder
+FROM alpine:3 as builder
 
 RUN apk add --no-cache ca-certificates curl
 
@@ -9,7 +9,7 @@ RUN curl -sL https://storage.googleapis.com/kubernetes-release/release/v${KUBECT
     -o /usr/local/bin/kubectl && chmod +x /usr/local/bin/kubectl && \
     kubectl version --client=true
 
-FROM alpine:3.19 as flux-cli
+FROM alpine:3 as flux-cli
 
 RUN apk add --no-cache ca-certificates