Bump third_party/imgui/repo from 277ae93 to fbf45ad (project-chip#32402)

Bumps [third_party/imgui/repo](https://github.com/ocornut/imgui) from `277ae93` to `fbf45ad`.
- [Release notes](https://github.com/ocornut/imgui/releases)
- [Commits](ocornut/imgui@277ae93...fbf45ad)

---
updated-dependencies:
- dependency-name: third_party/imgui/repo
  dependency-type: direct:production
...

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