Skip DNS rebind protection for health check endpoint

* Ensure host authorization excludes requests to the health check endpoint
* The PR is failing because the health check isn't in the list of accepted hosts, we need to intentionally exclude them

Author: sarahseewhy

config/environments/production.rb

@@ -76,7 +76,7 @@
   config.hosts = HostPatterns.allowed_host_patterns
 
   # Skip DNS rebinding protection for the default health check endpoint.
-  # config.host_authorization = { exclude: ->(request) { request.path == "/up" } }
+  config.host_authorization = { exclude: ->(request) { request.path == "/up" } }
 
   # Set ActiveRecord Encryption keys
   if ENV.key? "KMS_KEY_ID"