Update electron-beta to 1.7.4 (#4072)

Casks/electron-beta.rb

@@ -1,11 +1,11 @@
 cask 'electron-beta' do
-  version '1.7.3'
-  sha256 '083388a2c3b4fabaea02d7a5f7ac1f87c70ce44a828585c7a84b238ea1f9973a'
+  version '1.7.4'
+  sha256 '86e8af97e5c0033984a61033fd5569e44b3b4fb7c3a502e3968a8e15ab71951d'
 
   # github.com/electron/electron was verified as official when first introduced to the cask
   url "https://github.com/electron/electron/releases/download/v#{version}/electron-v#{version}-darwin-x64.zip"
   appcast 'https://github.com/electron/electron/releases.atom',
-          checkpoint: 'f064337f1fcdc461719c4cc47625b4406811bc8415d255475aedf88b78c7cf75'
+          checkpoint: '2317e9017ab85f839c6759c0c0fb59b2f3139e700ae4921cc0b27996790a90bc'
   name 'Electron'
   homepage 'https://electron.atom.io/'