build(deps): update zstd-ruby requirement from ~> 1.5 to ~> 2.0

Updates the requirements on [zstd-ruby](https://github.com/SpringMT/zstd-ruby) to permit the latest version.
- [Release notes](https://github.com/SpringMT/zstd-ruby/releases)
- [Commits](SpringMT/zstd-ruby@v1.5.0.0...v2.0.0)

---
updated-dependencies:
- dependency-name: zstd-ruby
  dependency-version: 2.0.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile

@@ -8,5 +8,5 @@ gem "rdoc", "~> 6.3"
 gem "rubocop", "~> 1.12"
 unless RUBY_PLATFORM == 'java'
   gem 'brotli', '>= 0.5'
-  gem 'zstd-ruby', '~> 1.5'
+  gem 'zstd-ruby', '~> 2.0'
 end