fix: docker/demo/Dockerfile to reduce vulnerabilities (#771)

The following vulnerabilities are fixed with an upgrade: - https://snyk.io/vuln/SNYK-DEBIAN12-AOM-7197979 - https://snyk.io/vuln/SNYK-DEBIAN12-EXPAT-7855502 - https://snyk.io/vuln/SNYK-DEBIAN12-KRB5-7411315 - https://snyk.io/vuln/SNYK-DEBIAN12-KRB5-7411315 - https://snyk.io/vuln/SNYK-DEBIAN12-KRB5-7411315 Co-authored-by: snyk-bot <snyk-bot@snyk.io>

Author: wayneeseguin

docker/demo/Dockerfile

@@ -1,4 +1,4 @@
-FROM nginx:1.25
+FROM nginx:1.27.3
 COPY htdocs /var/lib/data/demo/htdocs
 COPY init /init
 COPY nginx.conf /etc/nginx/conf.d/default.conf