Remove generated i18n files that should be gitignored

These files are generated by 'rake react_on_rails:locale' and are
already in .gitignore. They were mistakenly committed during the
Rspack migration when the build was failing.

CI runs 'bundle exec rake react_on_rails:locale' before building,
which generates these files from Rails i18n YAML files.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808