KDSoapWSDiscoveryClientConfig.cmake.in: Add KDSoap to dependencies

Otherwise, revdeps (like kio-extras samba support) fail at cmake step:

CMake Error at smb/CMakeLists.txt:72 (add_library):
  Target "kio_smb" links to target "KDSoap::kdsoap" but the target was not
  found.  Perhaps a find_package() call is missing for an IMPORTED target, or
  an ALIAS target is missing?

CMake Error at smb/CMakeLists.txt:57 (add_library):
  Target "kio_smb_static" links to target "KDSoap::kdsoap" but the target was
  not found.  Perhaps a find_package() call is missing for an IMPORTED
  target, or an ALIAS target is missing?