Core/VideoCommon: Fix duplicate OSD Custom Textures messages

Resolves duplicate OSD messages for Loading and Found custom textures.
VideoBackend initialization results in HiresTexture::Init being called.
We already call HiresTexture::Update when OnNewTitleLoad is called.
Thus we can remove HiresTextures::Init completely as it is redundant.

Source/Core/VideoCommon/HiresTextures.cpp

@@ -77,11 +77,6 @@ std::pair<std::string, bool> GetNameArbPair(const TextureInfo& texture_info)
 }
 }  // namespace
 
-void HiresTexture::Init()
-{
-  Update();
-}
-
 void HiresTexture::Shutdown()
 {
   Clear();