Move performance gem dependency into plugins config

Started getting this warning from latest Rubocop version:

```
rubocop-performance extension supports plugin, specify `plugins: rubocop-performance` instead of `require: rubocop-performance` in /home/runner/work/bridgetown-seo-tag/bridgetown-seo-tag/vendor/bundle/ruby/3.4.0+1/gems/rubocop-bridgetown-0.6.1/.rubocop.yml
```