setup order on Mac about CocoaPods is incomplete

### Page URL

https://docs.flutter.dev/get-started/install/macos/desktop/

### Page source

https://github.com/flutter/website/tree/main/src/content/get-started/install/macos/desktop.md

### Describe the problem

Mac is coming with ruby 2.0.6

simply running `sudo gem install cocoapods` as mentioned in the cocoapods step doesn't work

```
ERROR: Error installing cocoapods:
The last version of drb (>= 0) to support your Ruby & RubyGems was 2.0.6. Try installing it with `gem install drb -v 2.0.6` and then running the current command again
drb requires Ruby version >= 2.7.0. The current ruby version is 2.6.10.210.
```

### Expected fix

be able to provide context or additional note about the case. do we need to install ruby first? or run `gem install dry -v 2.0.6`?

### Additional context

_No response_

### I would like to fix this problem.

- [ ] I will try and fix this problem on docs.flutter.dev.