Update rake requirement from ~> 10.0 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

sensu-plugins-postgres.gemspec

@@ -47,7 +47,7 @@ Gem::Specification.new do |s| # rubocop:disable Metrics/BlockLength
   # locked to keep ruby 2.1 support, this is pulled in by test-kitchen
   s.add_development_dependency 'mixlib-shellout',           ['< 2.3.0', '~> 2.2']
   s.add_development_dependency 'pry',                       '~> 0.10'
-  s.add_development_dependency 'rake',                      '~> 10.0'
+  s.add_development_dependency 'rake',                      '~> 12.3'
   s.add_development_dependency 'redcarpet',                 '~> 3.2'
   s.add_development_dependency 'rspec',                     '~> 3.1'
   s.add_development_dependency 'rubocop',                   '~> 0.49.0'