Update sensu-plugin requirement from ~> 1.2 to >= 1.2, < 5.0

Updates the requirements on [sensu-plugin](https://github.com/sensu-plugins/sensu-plugin) to permit the latest version.
- [Release notes](https://github.com/sensu-plugins/sensu-plugin/releases)
- [Changelog](https://github.com/sensu-plugins/sensu-plugin/blob/master/CHANGELOG.md)
- [Commits](sensu-plugins/sensu-plugin@v1.2.0...3.0.1)

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

sensu-plugins-solr.gemspec

@@ -30,7 +30,7 @@ Gem::Specification.new do |s|
   s.test_files             = s.files.grep(%r{^(test|spec|features)/})
   s.version                = SensuPluginsSolr::Version::VER_STRING
 
-  s.add_runtime_dependency 'sensu-plugin', '~> 1.2'
+  s.add_runtime_dependency 'sensu-plugin', '>= 1.2', '< 5.0'
   s.add_runtime_dependency 'crack',             '= 0.4.3'
   s.add_runtime_dependency 'rest-client',       '1.8.0'
   s.add_runtime_dependency 'nokogiri',          '1.6.8.1'