Update Gemfile.devtools from dry-rb/template-gem

Author: File Sync

Gemfile.devtools

@@ -13,5 +13,5 @@ group :test do
 end
 
 group :tools do
-  gem "rubocop", "~> 1.38.0"
+  gem "rubocop", "~> 1.39.0"
 end