Embed this gem until gitlab moved to 7.x version

--- a/Gemfile
+++ b/Gemfile
@@ -139,7 +139,7 @@
 
 # Search
 gem 'elasticsearch-model', '~> 6.1', path: 'vendor/gems/elasticsearch-model'
-gem 'elasticsearch-rails', '~> 6.1', require: 'elasticsearch/rails/instrumentation'
+gem 'elasticsearch-rails', '~> 6.1', require: 'elasticsearch/rails/instrumentation', path: 'vendor/gems/elasticsearch-rails'
 gem 'elasticsearch-api',   '~> 6.8','>= 6.8.2'
 gem 'aws-sdk-core', '~> 3'
 gem 'aws-sdk-cloudformation', '~> 1'