blocksat-cli: disable failed test (#430851)

pkgs/development/python-modules/blocksat-cli/default.nix

···
     # Non-NixOS package managers are not present in the build environment.
     "test_parse_upgradable_list_apt"
     "test_parse_upgradable_list_dnf"
+    # Fails due to GPG clearsign output lacking trailing newline in some setups.
+    "test_clearsign_verification"
   ];
 
   disabledTestPaths = [ "blocksatgui/tests/" ];