Examples: DirectX12: Tweaked assertion to more accurately represent what it wants to say. (#301)

examples/directx12_example/imgui_impl_dx12.cpp

@@ -471,7 +471,7 @@ static void ImGui_ImplDX12_CreateFontsTexture()
     }
 
     // Store our identifier
-    static_assert(sizeof(void*) >= sizeof(g_hFontSrvGpuDescHandle.ptr), "Can't pack descriptor handle into TexID");
+    static_assert(sizeof(ImTextureID) >= sizeof(g_hFontSrvGpuDescHandle.ptr), "Can't pack descriptor handle into TexID");
     io.Fonts->TexID = (void *)g_hFontSrvGpuDescHandle.ptr;
 }