Drop redlock v1

Since #57 the lock
manager is expecting `redis-client` instance instead of `redis`.
`redis-client` is supported since redlock 2.0.0

References:
- https://github.com/leandromoreira/redlock-rb/blob/main/CHANGELOG.md#200---2023-02-09
- leandromoreira/redlock-rb#127

activejob-uniqueness.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = '>= 2.5'
 
   spec.add_dependency 'activejob', '>= 4.2', '< 7.2'
-  spec.add_dependency 'redlock', '>= 1.2', '< 3'
+  spec.add_dependency 'redlock', '>= 2.0', '< 3'
 
   spec.add_development_dependency 'appraisal', '~> 2.3.0'
   spec.add_development_dependency 'bundler', '>= 2.0'