fix test that relied on slow garbage collection (#903)

Co-authored-by: Çağtay Fabry <cagtay.fabry@bam.de>

weldx/tests/asdf_tests/test_weldx_file.py

@@ -449,7 +449,8 @@ def get_mem_info():
             # pytest increases memory a bit, but not as much as our large array would
             # occupy in memory.
             assert diff <= large_array.nbytes * 1.1, diff / 1024**2
-        assert np.all(WeldxFile(fn)["x"] == large_array)
+        with WeldxFile(fn) as wf:
+            assert np.all(wf["x"] == large_array)
 
     @staticmethod
     @pytest.mark.parametrize("mode", ("r", "rw"))