Update rake requirement from ~> 11.0 to ~> 12.3

Updates the requirements on [rake](https://github.com/ruby/rake) to permit the latest version.
- [Release notes](https://github.com/ruby/rake/releases)
- [Changelog](https://github.com/ruby/rake/blob/master/History.rdoc)
- [Commits](https://github.com/ruby/rake/commits/v12.3.1)

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

Author: dependabot-support

split-analytics.gemspec

@@ -19,5 +19,5 @@ Gem::Specification.new do |gem|
   gem.add_dependency('split', '>= 1.0.0')
 
   gem.add_development_dependency('rspec', '~> 3.1')
-  gem.add_development_dependency('rake', '~> 11.0')
+  gem.add_development_dependency('rake', '~> 12.3')
 end