Update airmail-beta to 3.3.3.446,311 (#4218)

Casks/airmail-beta.rb

@@ -1,11 +1,11 @@
 cask 'airmail-beta' do
-  version '3.3.3.445,309'
-  sha256 '04669fdc15ff1b6be66ef369bea55b3cc17f385673adaa94565d15ff2e4bc044'
+  version '3.3.3.446,311'
+  sha256 'bdb180dc5005ddfc5d7158b947446c5ce4a6191d6407775e9a9a9b294f3f92b6'
 
   # hockeyapp.net/api/2/apps/84be85c3331ee1d222fd7f0b59e41b04 was verified as official when first introduced to the cask
   url "https://rink.hockeyapp.net/api/2/apps/84be85c3331ee1d222fd7f0b59e41b04/app_versions/#{version.after_comma}?format=zip&"
   appcast 'https://rink.hockeyapp.net/api/2/apps/84be85c3331ee1d222fd7f0b59e41b04',
-          checkpoint: '4721a3ffb702fac31f4ca74420819ddc0bde92a676f52fb1cb0a05ddcae7c633'
+          checkpoint: 'fd3d80f29205536425a531eec669754febe2fc366bce3bd9f7f30fbfa184e1f3'
   name 'Airmail'
   homepage 'http://airmailapp.com/beta/'