Update atom-beta to 1.19.0-beta1 (#4016)

Casks/atom-beta.rb

@@ -1,11 +1,11 @@
 cask 'atom-beta' do
-  version '1.19.0-beta0'
-  sha256 'e66eee6851a4831b1490fe5634053f1c7280cc0428d34759ad72ee1579627927'
+  version '1.19.0-beta1'
+  sha256 '6a853f4b5e8734bfd5e4126eec158a36b97639eb7ede7b71538951397e599a86'
 
   # github.com/atom/atom was verified as official when first introduced to the cask
   url "https://github.com/atom/atom/releases/download/v#{version}/atom-mac.zip"
   appcast 'https://github.com/atom/atom/releases.atom',
-          checkpoint: '3979bb3f71ac479c0a6cb362996db3f471599e9f329d913a315302ce4aa32df2'
+          checkpoint: '87135fecea7358a3412a9010a0e30cbe08c2cc4e6b181505e9d774900c1731a4'
   name 'Github Atom Beta'
   homepage 'https://atom.io/beta'