test: restore dftu_core_test unit test

Author: dyzheng

source/source_lcao/module_dftu/test/CMakeLists.txt

@@ -78,12 +78,11 @@ AddTest(
   SOURCES dftu_pw_test.cpp
 )
 
-# Temporarily disabled for CI testing
-# AddTest(
-#   TARGET dftu_core_test
-#   LIBS ${math_libs} base device
-#   SOURCES dftu_core_test.cpp
-# )
+AddTest(
+  TARGET dftu_core_test
+  LIBS ${math_libs} base device
+  SOURCES dftu_core_test.cpp
+)
 
 AddTest(
   TARGET dftu_operator_test