Remove deprecated call to ImGui::GetKeyIndex

[LAK132]

No description provided.

[Fahersto]

I'm running into issues with ImGUi::GetKeyIndex as well.

imgui.cpp:(.text+0x175f0): multiple definition of `ImGui::GetKeyIndex(ImGuiKey)'; core/libcore.a(imgui_node_editor.cpp.o):imgui_node_editor.cpp:(.text+0x70f0): first defined here

I commented out the definition inside imgui_node_editor.cpp to make it work:
// namespace ImGui {
// ImGuiKey GetKeyIndex(ImGuiKey key)
// {
// IM_ASSERT(IsNamedKey(key));
// return key; // already the correct 'index' in modern ImGui
// }
// }