🧪 Enable memory leak tests on Python 3.14 (#7330)

Remove the skip markers from the engine memory leak tests.
These were added when `pympler.muppy.get_objects` caused the
suite to hang on Python 3.12.

Author: agoscinski

tests/engine/test_memory_leaks.py

@@ -8,8 +8,6 @@
 ###########################################################################
 """Utilities for testing memory leakage."""
 
-import sys
-
 import pytest
 
 from aiida import orm
@@ -44,15 +42,13 @@ def check_memory_leaks():
     assert not process_instances, f'Memory leak: process instances remain in memory: {process_instances}'
 
 
-@pytest.mark.skipif(sys.version_info >= (3, 12), reason='Garbage collecting hangs on Python 3.12')
 @pytest.mark.usefixtures('aiida_profile', 'check_memory_leaks')
 def test_leak_run_process():
     """Test whether running a dummy process leaks memory."""
     inputs = {'a': orm.Int(2), 'b': orm.Str('test')}
     run_finished_ok(test_processes.DummyProcess, **inputs)
 
 
-@pytest.mark.skipif(sys.version_info >= (3, 12), reason='Garbage collecting hangs on Python 3.12')
 @pytest.mark.usefixtures('aiida_profile', 'check_memory_leaks')
 def test_leak_local_calcjob(aiida_code_installed):
     """Test whether running a local CalcJob leaks memory."""
@@ -64,7 +60,6 @@ def test_leak_local_calcjob(aiida_code_installed):
     run_finished_ok(ArithmeticAddCalculation, **inputs)
 
 
-@pytest.mark.skipif(sys.version_info >= (3, 12), reason='Garbage collecting hangs on Python 3.12')
 @pytest.mark.usefixtures('aiida_profile', 'check_memory_leaks')
 def test_leak_ssh_calcjob(aiida_computer_ssh):
     """Test whether running a CalcJob over SSH leaks memory.