Merge branch 'update-health-check-gem' into 'master'

Update the health_check gem to the latest release

## What does this MR do?
Update the health_check gem to the latest release, which allows us to drop some of our code for overwriting the email check

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [ ] ~~API support added~~
- Tests
  - [ ] ~~Added for this feature/bug~~
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5186

CHANGELOG

@@ -31,6 +31,7 @@ v 8.10.0 (unreleased)
   - Exclude email check from the standard health check
   - Updated layout for Projects, Groups, Users on Admin area !4424
   - Fix changing issue state columns in milestone view
+  - Update health_check gem to version 2.1.0
   - Add notification settings dropdown for groups
   - Wildcards for protected branches. !4665
   - Allow importing from Github using Personal Access Tokens. (Eric K Idema)

Gemfile

@@ -344,7 +344,7 @@ gem 'oauth2', '~> 1.2.0'
 gem 'paranoia', '~> 2.0'
 
 # Health check
-gem 'health_check', '~> 1.5.1'
+gem 'health_check', '~> 2.1.0'
 
 # System information
 gem 'vmstat', '~> 2.1.0'

Gemfile.lock

@@ -322,8 +322,8 @@ GEM
       thor
       tilt
     hashie (3.4.3)
-    health_check (1.5.1)
-      rails (>= 2.3.0)
+    health_check (2.1.0)
+      rails (>= 4.0)
     hipchat (1.5.2)
       httparty
       mimemagic
@@ -870,7 +870,7 @@ DEPENDENCIES
   grape (~> 0.13.0)
   grape-entity (~> 0.4.2)
   hamlit (~> 2.5)
-  health_check (~> 1.5.1)
+  health_check (~> 2.1.0)
   hipchat (~> 1.5.0)
   html-pipeline (~> 1.11.0)
   httparty (~> 0.13.3)

config/initializers/health_check.rb

-# Email forcibly included in the standard checks, but the email health check
-# doesn't support the full range of SMTP options, which can result in failures
-# for valid SMTP configurations.
-# Overwrite the HealthCheck's detection of whether email is configured
-# in order to avoid the email check during standard checks
-module HealthCheck
-  class Utils
-    def self.mailer_configured?
-      false
-    end
-  end
-end
-
 HealthCheck.setup do |config|
   config.standard_checks = ['database', 'migrations', 'cache']
   config.full_checks = ['database', 'migrations', 'cache']