Update to Ruby 3.3

This is due to the fact that on Upsun/Platform.sh PHP 8.5 comes packaged with that Ruby version

Gemfile

@@ -1,5 +1,5 @@
 source "https://rubygems.org"
 
-ruby '>= 3.1', '< 3.2'
+ruby '>= 3.3', '< 3.4'
 
 gem "html-proofer", "~> 5.2"

Gemfile.lock

@@ -81,7 +81,7 @@ DEPENDENCIES
   html-proofer (~> 5.2)
 
 RUBY VERSION
-   ruby 3.1.2p20
+   ruby 3.3.10p183
 
 BUNDLED WITH
    2.6.5

docker/ruby/Dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:3.1.2-slim-bullseye
+FROM ruby:3.3.10-slim
 
 RUN apt-get update \
     && apt-get install -y \