add method in SyslogWrapper from ::Logger

it doesn't need to be set, it's just called sometimes

Change-Id: Ifcc08fb2f4a7645326f666f24dfc4de093c2c6a5
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/235562
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Ethan Vizitei <evizitei@instructure.com>
Product-Review: Ethan Vizitei <evizitei@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

lib/syslog_wrapper.rb

@@ -23,6 +23,8 @@ class SyslogWrapper
 
   attr_accessor :level, :datetime_format
 
+  def formatter; nil; end
+
   @@silencer = true
   def self.silencer; @@silencer; end
   def silencer; @@silencer; end