operations: fix multithread copy test to use the correct modify window

In bde0334bd8 "operations: fix setting the timestamp on Windows
for multithread copy" the test for multithread copy failed to take
into account the modify window of the remote under test.

fs/operations/multithread_test.go

@@ -138,7 +138,7 @@ func TestMultithreadCopy(t *testing.T) {
 			assert.Equal(t, src.Size(), dst.Size())
 			assert.Equal(t, "file1", dst.Remote())
 
-			fstest.CheckItems(t, r.Flocal, file1)
+			fstest.CheckListingWithPrecision(t, r.Flocal, []fstest.Item{file1}, nil, fs.GetModifyWindow(r.Flocal, r.Fremote))
 			require.NoError(t, dst.Remove(context.Background()))
 		})
 	}