Set Sidekiq log level to warning

This sets the log level for Sidekiq to warning to avoid sending lots of
unnecessary generic logging, when we can track these in other ways via
the Sidekiq dashboard. Instead, we only need to send logs about errors
or problems that might need attention.

config/initializers/sidekiq.rb

@@ -2,6 +2,9 @@
 
 url = ENV.fetch("REDIS_URL", "redis://localhost:6379/1")
 
-Sidekiq.configure_server { |config| config.redis = { url: } }
+Sidekiq.configure_server do |config|
+  config.redis = { url: }
+  config.logger.level = Logger::WARN
+end
 
 Sidekiq.configure_client { |config| config.redis = { url: } }