Remove duplicated QDebug operator for GpgME::Key
It is part of debug.h since 0a90ffb7 hence in some situations compilation fails with "ambiguous overload for ‘operator<<’ (operand types are ‘QDebug’ and ‘const GpgME::Key’)"
It is part of debug.h since 0a90ffb7 hence in some situations compilation fails with "ambiguous overload for ‘operator<<’ (operand types are ‘QDebug’ and ‘const GpgME::Key’)"