GPU: Drop OpenGL ES renderer

We can put this through the normal GL renderer instead.

src/core/gpu.h

@@ -155,9 +155,6 @@ public:
   // gpu_hw_opengl.cpp
   static std::unique_ptr<GPU> CreateHardwareOpenGLRenderer();
 
-  // gpu_hw_opengl_es.cpp
-  static std::unique_ptr<GPU> CreateHardwareOpenGLESRenderer();
-
   // gpu_sw.cpp
   static std::unique_ptr<GPU> CreateSoftwareRenderer();