Embed this gem until it is packaged

--- a/Gemfile
+++ b/Gemfile
@@ -310,7 +310,8 @@
 gem 'snowplow-tracker', '~> 0.6.1'
 
 # Memory benchmarks
-gem 'gitlab-derailed_benchmarks', require: false
+gem 'gitlab-derailed_benchmarks', require: false, path: 'vendor/gems/derailed-benchmarks'
+gem 'heapy', require: false
 
 # Metrics
 group :metrics do