Fix pipeline failures: NotImplementedError fetch_graph

What does this MR do and why?

Related upstream MR https://gitlab.com/gitlab-org/gitlab/-/commit/1336aa5c55923cc9d81f690dab33379afbcce0e0

Upstream removed fetch_graph method of app/controllers/projects/graphs_controller.rb, this method has been overridden by jh, which cause the pipeline failed.

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