Update message when sonar-scanner isn't installed

[Palleas]

Thanks for contributing to fastlane! Before you submit your pull request, please make sure to check the following boxes:

• Run bundle exec rspec from the subdirectory of each tool you modified. Alternatively, run rake test_all from the root directory.
• Run bundle exec rubocop -a to ensure the code style is valid
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• We currently don't accept new actions, please publish a plugin instead, more information in Plugins.md

The formula is now longer sonar-runner but sonar-scanner see the pull request in https://github.com/Homebrew/homebrew-core/search?q=sonar-runner&type=Issues&utf8=%E2%9C%93

[milch]

For posterity, sonar-runner was removed from brew here and replaced by sonar-scanner here

[milch]

🚀