Unquarantine value_streams_spec

What does this MR do and why?

Unquarntine ee/spec/requests/api/graphql/analytics/cycle_analytics/value_streams_spec.rb, which was quarantined yesterday in !164951 (merged) due to flakiness. The flakiness was resolved by @cablett in !164976 (merged) 🎉

Closes gitlab-org/quality/engineering-productivity/master-broken-incidents#8261 (closed)

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