update Dear ImGui to 1.91.8

extern/imgui_patched/backends/imgui_impl_dx10.cpp

@@ -49,7 +49,7 @@
 #pragma comment(lib, "d3dcompiler") // Automatically link with d3dcompiler.lib as we are using D3DCompile() below.
 #endif
 
-// DirectX data
+// DirectX10 data
 struct ImGui_ImplDX10_Data
 {
     ID3D10Device*               pd3dDevice;