Update dropbox-beta.rb (#3043)

* Update dropbox-beta.rb

* Update dropbox-beta.rb

* Update dropbox-beta.rb

Casks/dropbox-beta.rb

@@ -1,11 +1,11 @@
 cask 'dropbox-beta' do
-  version '17.3.27'
+  version '17.3.28'
-  sha256 'f5b5097e97177c20561e86a9fe2130488feff2727ebe8b5f662c5807e0f7c49b'
+  sha256 'ca3bb28124339420a13f4470329ee437a2a8f2fef0091ceb704f3610de96d17d'
 
   # clientupdates.dropboxstatic.com was verified as official when first introduced to the cask
   url "https://clientupdates.dropboxstatic.com/client/Dropbox%20#{version}.dmg"
   appcast 'https://www.dropbox.com/release_notes/rss.xml',
-          checkpoint: 'bc6e6e917ade0cadefdf23611c726afd4c362a9758062063457e2afed05b5181'
+          checkpoint: '8ff3fbcd6b128f85c7b530010b8b42e24aba486303e976552f0ed975af077abf'
   name 'Dropbox'
   homepage 'https://www.dropboxforum.com/t5/Desktop-client-builds/bd-p/101003016'