Fix warnings on Rails boot (#16946)

app/lib/sidekiq_error_handler.rb

@@ -1,26 +0,0 @@
-# frozen_string_literal: true
-
-class SidekiqErrorHandler
-  BACKTRACE_LIMIT = 3
-
-  def call(*)
-    yield
-  rescue Mastodon::HostValidationError
-    # Do not retry
-  rescue => e
-    limit_backtrace_and_raise(e)
-  ensure
-    socket = Thread.current[:statsd_socket]
-    socket&.close
-    Thread.current[:statsd_socket] = nil
-  end
-
-  private
-
-  # rubocop:disable Naming/MethodParameterName
-  def limit_backtrace_and_raise(e)
-    e.set_backtrace(e.backtrace.first(BACKTRACE_LIMIT))
-    raise e
-  end
-  # rubocop:enable Naming/MethodParameterName
-end