Merge pull request #10013 from pirj/fix-subdepartment-cop-docs-genera…

…tion

Fix sub-department cop doc generation

lib/rubocop/cop/documentation.rb

@@ -8,7 +8,7 @@ module Documentation
 
       # @api private
       def department_to_basename(department)
-        "cops_#{department.downcase}"
+        "cops_#{department.to_s.downcase.tr('/', '_')}"
       end
 
       # @api private