fix: Remove Humanizer dependency to prevent FileNotFoundException

[sentry]

This PR addresses a System.IO.FileNotFoundException that occurred when the application attempted to load the Humanizer.dll assembly at runtime, specifically when displaying dialogs that used its Humanize() extension method (e.g., BadMidiReadView and ErrorContentView).

The root cause was identified as the Humanizer.dll failing to resolve dynamically from the single-file executable bundle. To fix this, the Humanizer.Core NuGet package has been removed, and its minimal functionality (converting PascalCase strings to human-readable format) has been replaced with a custom StringExtensions.Humanize() method.

Changes include:

• Removed Humanizer.Core package reference from AutoMidiPlayer.WPF.csproj.
• Updated THIRD-PARTY-LICENSES.md to remove the Humanizer entry.
• Created AutoMidiPlayer.WPF/Helpers/StringExtensions.cs with a custom Humanize() extension method.
• Updated AutoMidiPlayer.WPF/Dialogs/BadMidiReadDialog/BadMidiReadView.xaml.cs and AutoMidiPlayer.WPF/Dialogs/ErrorContentDialog/ErrorContentView.xaml.cs to use the new custom extension method and remove the using Humanizer; directive.

Fixes AUTOMIDIPLAYER-T