Fix building against the latest Vulkan headers.

Bug: https://bugs.gentoo.org/721954
Bug: https://bugzilla.libsdl.org/show_bug.cgi?id=5227

--- a/src/video/SDL_vulkan_utils.c      2020-03-10 21:36:18.000000000 -0400
+++ b/src/video/SDL_vulkan_utils.c      2020-06-14 21:49:15.780898839 -0400
@@ -85,7 +85,9 @@
     case VK_ERROR_INVALID_SHADER_NV:
         return "VK_ERROR_INVALID_SHADER_NV";
     case VK_RESULT_MAX_ENUM:
+#if VK_HEADER_VERSION < 140
     case VK_RESULT_RANGE_SIZE:
+#endif
         break;
     }
     if(result < 0)