Update dependency chef to v19

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Gemfile

@@ -3,7 +3,7 @@
 source 'https://rubygems.org'
 
 gem 'berkshelf', '~> 8.0'
-gem 'chef', '~> 18.0'
+gem 'chef', '~> 19.0'
 
 group :test do
   gem 'bundler', '~> 2.0'