Embed this gem until gitlab moved to 7.x version

--- a/Gemfile
+++ b/Gemfile
@@ -128,7 +128,7 @@
 
 # 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'
 gem 'aws-sdk'
 gem 'faraday_middleware-aws-signers-v4'