Move Q_DECLARE_OPERATORS_FOR_FLAGS out of Kleo namespace

Declaring the global operator|() functions for those flags in the Kleo
namespace shadows the declaration of those functions for other flags
outside of the Kleo namespace.

(cherry picked from commit 6ac7b849ffa8cbe8fd0c945e7b3bb398d77024f4)

• GnuPG-bug-id: T7018