Update codebase for pluggy 1.0

[lava]

:notebook_with_decorative_cover: Description

The release of pluggy 1.0 broke threatbus, since we use type annotations for our arguments and the module containing the _HookRelay class was renamed from pluggy.hooks to pluggy._hooks.

:memo: Checklist

• [ ] All user-facing changes have changelog entries.
• [x] The changes are reflected on docs.tenzir.com/threatbus, if necessary.
• [x] The PR description contains instructions for the reviewer, if necessary.

:dart: Review Instructions