Configure JSON logs in production

This updates the configuration for Semantic Logger to output the JSON
logs to standard output, as per the instructions:

https://logger.rocketjob.io/rails.html#log-to-standard-out

config/environments/production.rb

@@ -52,6 +52,7 @@
   # Include generic and useful information about system operation, but avoid logging too much
   # information to avoid inadvertent exposure of personally identifiable information (PII).
   config.log_level = :info
+  config.log_format = :json
 
   # Prepend all log lines with the following tags.
   config.log_tags = [:request_id]
@@ -77,9 +78,12 @@
   # config.logger = ActiveSupport::TaggedLogging.new(Syslog::Logger.new "app-name")
 
   if ENV["RAILS_LOG_TO_STDOUT"].present?
-    logger = ActiveSupport::Logger.new($stdout)
-    logger.formatter = config.log_formatter
-    config.logger = ActiveSupport::TaggedLogging.new(logger)
+    $stdout.sync = true
+    config.rails_semantic_logger.add_file_appender = false
+    config.semantic_logger.add_appender(
+      io: $stdout,
+      formatter: config.rails_semantic_logger.format,
+    )
   end
 
   # Do not dump schema after migrations.