Update .ruby-version to 3.2.2

[govuk-ci]

Upgrades Ruby to 3.2.2. See commits for more details.
This PR should be tested before merge, as per https://docs.publishing.service.gov.uk/manual/ruby.html#update-ruby-version-in-the-relevant-repos.

Trello card: https://trello.com/c/K1grjTiC/3373-upgrade-ruby-versions-to-322-2

[floehopper]

I see the following deprecation warning in the test log:

WARNING: MYSQL_OPT_RECONNECT is deprecated and will be removed in a future version.

However, this seems to have been there before the Ruby version bump.

Looking into it more closely, it seems as if the problem lies with the mysql2 gem which sets MYSQL_OPT_RECONNECT to false even if the reconnect option is not specified in database.yml. See this code. Given that others have already raised an issue, I'd assume this will be fixed at least by the time MySQL removes the option altogether. So I don't think any action is required by us for now.

[floehopper]

I deployed this branch to integration and clicked around the app a bit. I didn't see any problems with the app's behaviour, I didn't see any spike in errors in the Graphana dashboard, and I didn't see any exceptions reported in Sentry. So I think this is good to merge.