Update nginxinc/nginx-unprivileged Docker tag to v1.31

Author: renovate[bot]

Dockerfile

@@ -1,5 +1,5 @@
 # syntax=docker/dockerfile:1
-FROM nginxinc/nginx-unprivileged:1.27-alpine
+FROM nginxinc/nginx-unprivileged:1.31-alpine
 WORKDIR /usr/share/nginx/html/
 
 # copy the entire application

DockerfileLocal

@@ -26,7 +26,7 @@ RUN mkdocs build
 # remove the build theme because it is not needed after site is build.
 RUN rm -rf dist
 
-FROM nginxinc/nginx-unprivileged:1.27-alpine as deploy
+FROM nginxinc/nginx-unprivileged:1.31-alpine as deploy
 COPY --from=builder $HOME/application/site/ /usr/share/nginx/html/
 COPY default.conf /etc/nginx/conf.d/