Vulkan: disable explicitlyCastMediumpFloatTo16Bit for Venus Workaround for platforms shipping Venus until vk-gl-cts issue 4554 gets resolved. Bug: b/290425152 Test: CtsSkQPTestCases org.skia.skqp.SkQPRunner#gles_gradient_many_stops Change-Id: Ia05d905a9b56264164ed3325e4966dd2976b1fe9 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4684548 Auto-Submit: Yiwei Zhang <zzyiwei@chromium.org> Commit-Queue: Yiwei Zhang <zzyiwei@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>