Use release specific repo for NGINX Plus on Debian (#2051)

Author: lucacome

build/Dockerfile

@@ -46,7 +46,7 @@ RUN --mount=type=secret,id=nginx-repo.crt,dst=/etc/ssl/nginx/nginx-repo.crt,mode
 	&& curl -sSL https://cs.nginx.com/static/keys/nginx_signing.key | gpg --dearmor > /etc/apt/trusted.gpg.d/nginx_signing.gpg \
 	&& curl -sSL -o /etc/apt/apt.conf.d/90pkgs-nginx https://cs.nginx.com/static/files/90pkgs-nginx \
 	&& printf "%s\n" "Acquire::https::pkgs.nginx.com::User-Agent  \"k8s-ic-$IC_VERSION-apt\";" >> /etc/apt/apt.conf.d/90pkgs-nginx \
-	&& printf "%s\n" "deb https://pkgs.nginx.com/plus/debian buster nginx-plus" > /etc/apt/sources.list.d/nginx-plus.list \
+	&& printf "%s\n" "deb https://pkgs.nginx.com/plus/${NGINX_PLUS_VERSION^^}/debian buster nginx-plus" > /etc/apt/sources.list.d/nginx-plus.list \
 	&& apt-get update \
 	&& apt-get install --no-install-recommends --no-install-suggests -y \
 	nginx-plus-${NGINX_PLUS_VERSION} nginx-plus-module-njs-${NGINX_PLUS_VERSION} \