fix: docker-examples/v5/reverse_proxy/nginx_relative/nginx/Dockerfile…

… to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE315-LIBWEBP-5902238
- https://snyk.io/vuln/SNYK-ALPINE315-NGHTTP2-5964211
- https://snyk.io/vuln/SNYK-ALPINE315-CURL-3320718
- https://snyk.io/vuln/SNYK-ALPINE315-CURL-5958915
- https://snyk.io/vuln/SNYK-ALPINE315-ZLIB-2976173

docker-examples/v5/reverse_proxy/nginx_relative/nginx/Dockerfile

@@ -1,2 +1,2 @@
-FROM nginx:1.21-alpine
+FROM nginx:1.26.1-alpine
 COPY nginx/default.conf /etc/nginx/conf.d/default.conf