GaudiPolicy: migrate to pytest

GaudiPolicy/CMakeLists.txt

 #####################################################################################
-# (c) Copyright 1998-2019 CERN for the benefit of the LHCb and ATLAS collaborations #
+# (c) Copyright 1998-2023 CERN for the benefit of the LHCb and ATLAS collaborations #
 #                                                                                   #
 # This software is distributed under the terms of the Apache version 2 licence,     #
 # copied verbatim in the file "LICENSE".                                            #
@@ -21,6 +21,5 @@ if(BUILD_TESTING)
     # https://its.cern.ch/jira/browse/GAUDI-976
     gaudi_add_tests(QMTest ${CMAKE_CURRENT_SOURCE_DIR}/tests/GAUDI-976)
 
-    # nosetests
-    gaudi_add_tests(nosetests ${CMAKE_CURRENT_SOURCE_DIR}/python/GaudiTesting)
+    gaudi_add_tests(pytest ${CMAKE_CURRENT_SOURCE_DIR}/python/GaudiTesting)
 endif()