render tests: fixed render tests to not use gl_FragColor
render tests: fixed render tests to not use gl_FragColor

gl_FragColor was eliminated in GLSL 1.3.

sashinde/VulkanTools,KhronosGroup/Vulkan-LoaderAndValidationLayers,Radamanthe/VulkanSamples,elongbug/Vulkan-LoaderAndValidationLayers,critsec/Vulkan-LoaderAndValidationLayers,critsec/Vulkan-LoaderAndValidationLayers,Radamanthe/VulkanSamples,KhronosGroup/Vulkan-LoaderAndValidationLayers,critsec/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,Radamanthe/VulkanSamples,KhronosGroup/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,critsec/Vulkan-LoaderAndValidationLayers,Radamanthe/VulkanSamples,sashinde/VulkanTools,sashinde/VulkanTools,sashinde/VulkanTools,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples