Update ktfmt to 0.51 and resolve breaking changes

[simonhauck]

🚀 Description

This PR updates the ktfmt dependency and resolves the breaking changes of ktfmt.

The first commit updates the dependency and removes the FormattingOptions.Style since it is no longer supported by ktfmt.

The second commit removes the dropboxStyle() option since it is no longer available in ktfmt. Applications should use the kotlinLangStyle() instead. If you do not want to remove this option, you can revert the commit.

📄 Motivation and Context

Resolves #302 Solves this failing PR #299

🧪 How Has This Been Tested?

With the automatic CI

📦 Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)

✅ Checklist

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.

[ukarlsson]

Any chance this version could be released? Many thanks