Update sketch-beta to 43.1,39012 (#3607)

Casks/sketch-beta.rb

@@ -1,11 +1,11 @@
 cask 'sketch-beta' do
-  version '43,38998'
-  sha256 '134927c36a4e0f4bcc8ee454a6a75a7fe73f7cdd24f0d35f223509059910a2c7'
+  version '43.1,39012'
+  sha256 '3fbbb6b931f5ce7c89bb1500ef1b52b2bf7f6cc2f3a92c08429f9b88980c24cf'
 
   # hockeyapp.net/api/2/apps/0172d48cceec171249a8d850fb16276b was verified as official when first introduced to the cask
   url "https://rink.hockeyapp.net/api/2/apps/0172d48cceec171249a8d850fb16276b/app_versions/#{version.after_comma}?format=zip"
   appcast 'https://rink.hockeyapp.net/api/2/apps/0172d48cceec171249a8d850fb16276b',
-          checkpoint: '18c2b4692ca6ac143d48eeb95bed87d1ebf61d1f0eafbf8311918fa3f370e381'
+          checkpoint: '5fcfbfd7a527113fd175cda1239ed372e63e390cac8bcf4c2e05f14d3655bdc5'
   name 'Sketch'
   homepage 'https://www.sketchapp.com/beta/'