Update herb to v0.8

[r-plus]

Hi @r7kamura

Update herb v0.8 to support Ruby 4 precompiled binary.

looks like herb v0.8 is not contains breaking change for parser API.
https://github.com/marcoroth/herb/releases/tag/v0.8.0

[r7kamura]

@r-plus I couldn't understand the background for why the required version of herb in rubocop-erb needs to be changed. What is the reason for forcing users to use herb 0.8 or higher in rubocop-erb? Please provide a more detailed explanation.

To explain my question in more detail: if you want to use the precompiled binaries for Ruby 4.0 that you mentioned in your project, I believe you just need to upgrade the version of Herb to 0.8 or higher within your project. Since that should normally be enough, I don't yet understand why it is necessary to drop support for Herb versions below 0.8 in rubocop-erb side. It would be a different story if rubocop-erb were forcibly restricting it to versions of erb below 0.8 (e.g. < 0.8), but that’s not the case this time, is it?

[r-plus]

Ah sorry i misunderstood behavior of ~> 0.7, you are right.
We can update herb to v0.8 in our project.

[r7kamura]

I see, I'm glad we cleared up the misunderstanding. The tilde notation ~> in RubyGems is very confusing. I still make mistakes with it myself sometimes. Please don't worry about it. Thank you for trying to contribute 👍