Fixed cache key difference for graph

app/models/repository.rb

@@ -65,7 +65,7 @@ class Repository
   end
   def graph_log
-    Rails.cache.fetch(cache_key(:graph)) do
+    Rails.cache.fetch(cache_key(:graph_log)) do
       stats = Gitlab::Git::GitStats.new(raw, root_ref)
       stats.parsed_log
     end