Vulkan: Fix Shared Present Mode "acquireNextSwapchainImage()" - no need to call "vkAcquireNextImageKHR()" in Shared Present Mode. - proper VkResult processing (VK_SUBOPTIMAL_KHR replaced with VK_SUCCESS). Bug: angleproject:6878 Change-Id: Ib20ae1f5de3a3cc13bfc4ef034076e3402f93d31 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4489464 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Igor Nazarov <i.nazarov@samsung.com>