generate_cask_token with ruby 2.X

[rcmdnk]

generate_cask_token in homebrew-cask does now work with ruby 3.X

Homebrew/homebrew-cask#123053

Currently, the script is executed directly, so if the system has a PATH to ruby 3.X, it fails.

In addition, from homebrew 4.X, homebrew-cask is not tapped by default.

https://github.com/Homebrew/homebrew-cask/blob/c24db49e9489190949096156a1f97ee02c15c68b/developer/bin/generate_cask_token#L267

On the other hand, generate_cask_token just changes space to hyphen and upper letters to lower letters and a little more cleanups(and check if the cask already exists or not).
it may be better to do directly.