Fix warnings for UsageMetricDefinitionGenerator

config/application.rb

@@ -84,6 +84,7 @@ module Gitlab
     # Rake tasks ignore the eager loading settings, so we need to set the
     # autoload paths explicitly
     config.autoload_paths = config.eager_load_paths.dup
+    config.autoload_paths.push("#{config.root}/lib/generators") if Rails.env.development?
 
     # Only load the plugins named here, in the order given (default is alphabetical).
     # :all can be used as a placeholder for all plugins not explicitly named.

lib/generators/gitlab/usage_metric_definition/redis_hll_generator.rb

 # frozen_string_literal: true
 
 require 'rails/generators'
-require_relative '../usage_metric_definition_generator'
 
 module Gitlab
   module UsageMetricDefinition