renderer_opengl/utils: Remove unused includes and unused forward declaration

src/video_core/renderer_opengl/utils.h

@@ -8,13 +8,9 @@
 #include <vector>
 #include <glad/glad.h>
 #include "common/common_types.h"
-#include "common/math_util.h"
-#include "video_core/renderer_opengl/gl_resource_manager.h"
 
 namespace OpenGL {
 
-class CachedSurfaceView;
-
 class BindBuffersRangePushBuffer {
 public:
     BindBuffersRangePushBuffer(GLenum target);