video_core: set vertex buffer num to 16, because mvk have when using more than 16

src/video_core/buffer_cache/buffer_cache_base.h

@@ -62,7 +62,11 @@ using BufferId = SlotId;
 using VideoCore::Surface::PixelFormat;
 using namespace Common::Literals;
 
+#ifdef __APPLE__
+constexpr u32 NUM_VERTEX_BUFFERS = 16;
+#else
 constexpr u32 NUM_VERTEX_BUFFERS = 32;
+#endif
 constexpr u32 NUM_TRANSFORM_FEEDBACK_BUFFERS = 4;
 constexpr u32 NUM_GRAPHICS_UNIFORM_BUFFERS = 18;
 constexpr u32 NUM_COMPUTE_UNIFORM_BUFFERS = 8;