developer/bin/generate_cask_token: fix .sub! on non-string exception

[yurikoles]

Signed-off-by: Yurii Kolesnykov [email protected]

---

[yurikoles]

Before:

$ generate_cask_token "Windows App.app" 

homebrew/Library/Taps/homebrew/homebrew-cask/developer/bin/generate_cask_token:254:in `remove_trailing_strings_and_versions': undefined method `sub!' for an instance of AppName (NoMethodError)

      app_name.sub!(self.class.remove_trailing_pat, "")
              ^^^^^
	from /opt/homebrew/Library/Taps/homebrew/homebrew-cask/developer/bin/generate_cask_token:267:in `simplified'
	from /opt/homebrew/Library/Taps/homebrew/homebrew-cask/developer/bin/generate_cask_token:368:in `simplified_app_name'
	from /opt/homebrew/Library/Taps/homebrew/homebrew-cask/developer/bin/generate_cask_token:372:in `cask_file_name'
	from /opt/homebrew/Library/Taps/homebrew/homebrew-cask/developer/bin/generate_cask_token:376:in `cask_token'
	from /opt/homebrew/Library/Taps/homebrew/homebrew-cask/developer/bin/generate_cask_token:397:in `report'
	from /opt/homebrew/Library/Taps/homebrew/homebrew-cask/developer/bin/generate_cask_token:437:in `<main>'

After:

$ generate_cask_token "Windows App.app"
Proposed token:               windows
Proposed file name:           windows.rb
Cask Header Line:             cask "windows" do