tests: harden memory leak check in test_siblings_without_eval (#3088)

Signed-off-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>

python/tests/test_array.py

@@ -11,14 +11,10 @@ import weakref
 from copy import copy, deepcopy
 from itertools import permutations
 
-if platform.system() == "Windows":
-    import psutil
-else:
-    import resource
-
 import mlx.core as mx
 import mlx_tests
 import numpy as np
+import psutil
 
 try:
     import tensorflow as tf
@@ -2087,11 +2083,8 @@ class TestArray(mlx_tests.MLXTestCase):
 
     def test_siblings_without_eval(self):
         def get_mem():
-            if platform.system() == "Windows":
-                process = psutil.Process(os.getpid())
-                return process.memory_info().peak_wset
-            else:
-                return resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
+            process = psutil.Process(os.getpid())
+            return process.memory_info().rss
 
         key = mx.array([1, 2])