Update README.md

Author: moritzheiber

README.md

@@ -87,7 +87,7 @@ $ docker build \
   --build-arg IMAGE_NAME=ubuntu:22.04 \
   -t ruby-jemalloc:3.1.4-ubuntu-22.04 .
 ```
-_Note: Ruby `3.2.2-slim` is the default when building the Docker image without any build arguments._
+_Note: Ruby `3.3.0-slim` is the default when building the Docker image without any build arguments._
 
 ## Tests
 
@@ -100,7 +100,7 @@ dgoss run -ti ruby-jemalloc
 You can specify the Ruby version to test for by passing `RUBY_VERSION` as a variable:
 
 ```console
-dgoss run -ti -e RUBY_VERSION=3.2.2 ruby-jemalloc
+dgoss run -ti -e RUBY_VERSION=3.3.0 ruby-jemalloc
 ```
 
-_Note: `3.2.2` is the default. And don't forget to also pass the correct `RUBY_CHECKSUM`._
+_Note: `3.3.0` is the default. And don't forget to also pass the correct `RUBY_CHECKSUM`._