[vk] Fix Sample Shading to ensure it is properly enabled

Even when sample shading was enabled via settings, the pipeline was
configured with minSampleShading = 0.0f, effectively disabling the
feature.

This patch sets minSampleShading = 1.0f when sample shading is enabled,
ensuring that per-sample shading is actually used as intended.

src/video_core/renderer_vulkan/vk_graphics_pipeline.cpp

@@ -743,7 +743,7 @@ void GraphicsPipeline::MakePipeline(VkRenderPass render_pass) {
         .flags = 0,
         .rasterizationSamples = MaxwellToVK::MsaaMode(key.state.msaa_mode),
         .sampleShadingEnable = Settings::values.sample_shading.GetValue() ? VK_TRUE : VK_FALSE,
-        .minSampleShading = 0.0f,
+        .minSampleShading = Settings::values.sample_shading.GetValue() ? 1.0f : 0.0f,
         .pSampleMask = nullptr,
         .alphaToCoverageEnable = key.state.alpha_to_coverage_enabled != 0 ? VK_TRUE : VK_FALSE,
         .alphaToOneEnable = key.state.alpha_to_one_enabled != 0 ? VK_TRUE : VK_FALSE,