gl_shader_manager: Remove unnecessary gl_shader_manager inclusion

This isn't used at all in the OpenGL shader cache, so we can remove it's
include here, meaning one less file needs to be recompiled if any
changes ever occur within that header.

core/memory.h is also not used within this file at all, so we can remove
it as well.

src/video_core/renderer_opengl/gl_shader_cache.cpp

@@ -6,13 +6,11 @@
 #include "common/assert.h"
 #include "common/hash.h"
 #include "core/core.h"
-#include "core/memory.h"
 #include "video_core/engines/maxwell_3d.h"
 #include "video_core/renderer_opengl/gl_rasterizer.h"
 #include "video_core/renderer_opengl/gl_shader_cache.h"
 #include "video_core/renderer_opengl/gl_shader_decompiler.h"
 #include "video_core/renderer_opengl/gl_shader_disk_cache.h"
-#include "video_core/renderer_opengl/gl_shader_manager.h"
 #include "video_core/renderer_opengl/utils.h"
 #include "video_core/shader/shader_ir.h"