Remove download sha file from .metadata dir when uninstalling casks

Library/Homebrew/cask/installer.rb

@@ -403,7 +403,10 @@ module Cask
     def uninstall
       oh1 "Uninstalling Cask #{Formatter.identifier(@cask)}"
       uninstall_artifacts(clear: true)
-      remove_config_file if !reinstall? && !upgrade?
+      if !reinstall? && !upgrade?
+        remove_download_sha
+        remove_config_file
+      end
       purge_versioned_files
       purge_caskroom_path if force?
     end
@@ -413,6 +416,10 @@ module Cask
       @cask.config_path.parent.rmdir_if_possible
     end
 
+    def remove_download_sha
+      FileUtils.rm_f @cask.download_sha_path if @cask.download_sha_path.exist?
+    end
+
     def start_upgrade
       uninstall_artifacts
       backup