Prepare release v254

[heroku-linguist[bot]]

Commits since the last release:

• Bump the test-dependencies group across 1 directory with 2 updates
• Merge pull request #735 from heroku/dependabot/bundler/test-dependencies-f01c551da1
• Enable heroku-24 in Dev Center generator (#736)
• Sync conf/nginx/mime.types
• text/javascript MIME type for .mjs in Nginx config
• Merge pull request #740 from heroku/nginx-mime-updates
• bundle update
• composer update
• PHP/8.2.21
• PHP/8.3.9
• ext-newrelic/10.22.0.12
• ext-blackfire/1.92.18
• Blackfire/2.28.6
• Apache/2.4.61
• Blackfire/2.28.7
• Merge pull request #742 from heroku/develop

For the full diff, see the compare view: https://github.com/heroku/heroku-buildpack-php/compare/v253...main