fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN12-NGINX-5953391
- https://snyk.io/vuln/SNYK-DEBIAN12-ZLIB-6008963
- https://snyk.io/vuln/SNYK-DEBIAN12-AOM-7197979
- https://snyk.io/vuln/SNYK-DEBIAN12-AOM-6140324
- https://snyk.io/vuln/SNYK-DEBIAN12-GLIBC-1547196

Dockerfile

@@ -33,7 +33,7 @@ RUN bundle exec ./scripts/fetch-external-resources
 RUN make real_generate
 
 
-FROM nginx:1.25
+FROM nginx:1.26.1
 
 COPY --from=builder /usr/src/jenkinsio/build/_site /usr/share/nginx/html