[SB][Chips] Fix NotifChipsViewModelTest asserting same model instance

If we want to assert that the model is unchanged, we need to use the
same icon for the old notification and new one.

Fixes: 419214696
Bug: 393456147
Flag: TEST_ONLY
Test: atest NotifChipsViewModelTest
Change-Id: Ia041b2d194e835dfd7a1a3823ef918b99aa41d4f