Apply Homebrew formula test cleanup

Author: AndreyVMarkelov

packaging/homebrew/dbxcli.rb

@@ -14,7 +14,6 @@ def install
   end
 
   test do
-    ENV.delete "DBXCLI_ACCESS_TOKEN"
     ENV["DBXCLI_AUTH_FILE"] = testpath/"missing-auth.json"
     output = shell_output("#{bin}/dbxcli ls 2>&1", 1)
     assert_match "no saved Dropbox credentials", output