Update rbnacl requirement from ~> 7.0.0 to >= 7.0, < 7.2

Updates the requirements on [rbnacl](https://github.com/crypto-rb/rbnacl) to permit the latest version.
- [Release notes](https://github.com/crypto-rb/rbnacl/releases)
- [Changelog](https://github.com/crypto-rb/rbnacl/blob/master/CHANGES.md)
- [Commits](RubyCrypto/rbnacl@v7.0.0...v7.1.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

session_keys.gemspec

@@ -38,7 +38,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.add_dependency 'rbnacl', '~> 7.0.0'
+  spec.add_dependency 'rbnacl', '>= 7.0', '< 7.2'
   spec.add_dependency 'zxcvbn-ruby', '>= 1.0', '< 2.0'
 
   spec.add_development_dependency 'bundler'