Disable the email checking part of the standard Health Check

The email check used in the Heath Check doesn't properly make use of enough of the SMTP config options
to be able to properly test the STMP connection, and as a result could cause a failure.

In order to fix it we have overwritten the email_configured? method in the health check
so that it does not check email status during the standard health check.

CHANGELOG

@@ -5,6 +5,7 @@ v 8.10.0 (unreleased)
   - Add Sidekiq queue duration to transaction metrics.
   - Fix MR-auto-close text added to description. !4836
   - Fix pagination when sorting by columns with lots of ties (like priority)
+  - Exclude email check from the standard health check
   - Implement Subresource Integrity for CSS and JavaScript assets. This prevents malicious assets from loading in the case of a CDN compromise.
   - Fix user creation with stronger minimum password requirements !4054 (nathan-pmt)

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']
 end