VK_EXT_pipeline_creation_feedback: Invalid feedback is legal

VK_EXT_pipeline_creation_feedback: Invalid feedback is legal

The tests incorrectly required that
VK_PIPELINE_CREATION_FEEDBACK_VALID_BIT be set in
VkPipelineCreationFeedbackCreateInfo::pPipelineCreationFeedback.
However, the tests already and correctly permit the bit to be unset in
VkPipelineCreationFeedbackCreateInfo::pPipelineStageCreationFeedbacks.

The Vulkan 1.3.225 spec says:
    An implementation should write pipeline creation feedback to
    pPipelineCreationFeedback and may write pipeline stage creation
    feedback to pPipelineStageCreationFeedbacks. An implementation must
    set or clear the VK_PIPELINE_CREATION_FEEDBACK_VALID_BIT in
    VkPipelineCreationFeedback::flags for pPipelineCreationFeedback and
    every element of pPipelineStageCreationFeedbacks.

Components: Vulkan
VK-GL-CTS Issue: 3912
Affects:
dEQP-VK.pipeline.creation_feedback.*

Signed-off-by: Chad Versace <chadversary@google.com>
Change-Id: I4eb37b5888a4d780b4b0b12f9c65960aca9f7806