Use Ruby 3.2.2-alpine in Dockerfile

The Bundler Audit GitHub Action is currently failing in CI.

@laicuRoot has submitted a PR to the maintainer that fixes this by
updating the `Dockerfile` to use the latest available version of Ruby.

This commit applies the fix for us to use the action while waiting for
the upstream changes..

Ref:
- andrewmcodes#6

Dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:2.7.0-alpine
+FROM ruby:3.2.2-alpine
 
 COPY LICENSE README.md /
 COPY entrypoint.sh /entrypoint.sh