configure_graphics: Remove Force 30 FPS mode

The introduction of multicore rendered this setting non-functional as timing code was changed.

This removes the setting entirely.

src/yuzu/configuration/configure_graphics_advanced.h

@@ -38,5 +38,4 @@ private:
     ConfigurationShared::CheckState use_assembly_shaders;
     ConfigurationShared::CheckState use_asynchronous_shaders;
     ConfigurationShared::CheckState use_fast_gpu_time;
-    ConfigurationShared::CheckState force_30fps_mode;
 };