Fix egamma path in the tier 0 validation test
The Tier 0 histograms use Egamma as a path, rather than Electron, so this corrects the mistaken use of Electron, such that the histograms will be found
The Tier 0 histograms use Egamma as a path, rather than Electron, so this corrects the mistaken use of Electron, such that the histograms will be found