fix imgui delete function

[jimwang118]

Fixes

Description of the changes:

-Building with "tool" feature fails. ImGui's SetNextTreeNodeOpen was previously deprecated and now has been removed. Call SetNextItemOpen instead. see https://github.com/ocornut/imgui/blob/1362fc0c56d8742167379661a353d8342f7c4a86/imgui.h#L3131

Before submitting a Pull Request:

• [X] I reviewed CONTRIBUTING.md
• [X] I built my changes locally
• [X] I ran the unit tests
• [X] I ran the functional tests with a device
• [X] I ran the performance tests with a device

I tested changes on:

• [X] Windows
• [ ] Linux

[thundercarrot]

Any chance of finishing this up? Not sure what the issue is.

[FrankXie05]

@jaygullapalli