Update newrelic agent.

Move to the latest minor version of the NR plugin because 3.x removes some deprecated functions.

requirements/edx/base.txt

@@ -147,7 +147,7 @@ watchdog==0.8.3
 
 # Metrics gathering and monitoring
 dogapi==1.2.1
-newrelic==2.86.3.70
+newrelic==2.104.0.86
 
 # Used for documentation gathering
 sphinx==1.1.3