libs/vkd3d-shader: Get rid of VKD3D_SHADER_FLIP_Y compiler option.

We use negative viewport height to flip Y.

programs/vkd3d-compiler/main.c

@@ -89,7 +89,6 @@ static const struct
 }
 compiler_options[] =
 {
-    {"--flip-y", VKD3D_SHADER_FLIP_Y},
     {"--strip-debug", VKD3D_SHADER_STRIP_DEBUG},
 };
 
@@ -144,7 +143,7 @@ int main(int argc, char **argv)
     if (!parse_command_line(argc, argv, &options))
     {
         fprintf(stderr,
-                "usage: %s [--strip-degug] [--flip-y] [-o <out_spirv_filename>] <dxbc_filename>\n",
+                "usage: %s [--strip-degug] [-o <out_spirv_filename>] <dxbc_filename>\n",
                 argv[0]);
         return 1;
     }