Fix Multiplane aspect bit Immutable Sampler test

https://github.com/KhronosGroup/Vulkan-ValidationLayers/pull/5583 broke up the test into just `VkLayerTest.MultiplaneAspectBits` but currently it is not testing anything

The issue seems to be with how `IsImmutableSampler()` is returning in the validation check that it doesn't hit `VUID-VkDescriptorImageInfo-sampler-01564`

Need to investigate more if this is a test bug or layer bug

note - https://github.com/KhronosGroup/Vulkan-ValidationLayers/issues/1523

Start with the VkLayerTest.MultiplaneAspectBits test introduced by PR 5583 and trace the validation check involving IsImmutableSampler(). Compare its behavior with VUID-VkDescriptorImageInfo-sampler-01564 and the context in issue #1523. Done means determining whether the test or validation layer is faulty and restoring coverage of the intended validation error.

Written by the indexing model from the issue text.