grafana: fix yarn vendor hash (#401505)

  missingHashes = ./missing-hashes.json;

  offlineCache = yarn-berry_4.fetchYarnBerryDeps {

    inherit src missingHashes;

    hash = "sha256-qJ1xP02tdoZmAlrO5J8wxRYdNeg420NN27Tt2gaNPFc=";

    hash = "sha256-tpQjEa4xeD4fmrucynt8WVVXZ3uN5WxjSF8YcjE6HLU=";

  };

  disallowedRequisites = [ offlineCache ];