Remove newrelic gem. Closes #12860

Gemfile

@@ -303,8 +303,6 @@ group :production do
   gem "gitlab_meta", '7.0'
 end
-gem "newrelic_rpm", '~> 3.14'
-
 gem 'octokit', '~> 3.8.0'
 gem "mail_room", "~> 0.6.1"

Gemfile.lock

@@ -479,7 +479,6 @@ GEM
     net-ldap (0.12.1)
     net-ssh (3.0.1)
     netrc (0.11.0)
-    newrelic_rpm (3.14.1.311)
     nokogiri (1.6.7.2)
       mini_portile2 (~> 2.0.0.rc2)
     nprogress-rails (0.1.6.7)
@@ -960,7 +959,6 @@ DEPENDENCIES
   mysql2 (~> 0.3.16)
   nested_form (~> 0.3.2)
   net-ssh (~> 3.0.1)
-  newrelic_rpm (~> 3.14)
   nokogiri (= 1.6.7.2)
   nprogress-rails (~> 0.1.6.7)
   oauth2 (~> 1.0.0)

config/newrelic.yml

-# New Relic configuration file
-#
-# This file is here to make sure the New Relic gem stays
-# quiet by default.
-#
-# To enable and configure New Relic, please use
-# environment variables, e.g. NEW_RELIC_ENABLED=true
-
-production:
-  enabled: false
-
-development:
-  enabled: false
-
-test:
-  enabled: false