Bump third_party/imgui/repo from `3c435c0` to `092c88d` #2297

Job	Run time
Build on Linux (fake, gcc_release, clang, simulated)	2h 11m 56s
Build on Linux (gcc_debug)	1h 15m 2s
Build on Linux (python_lib)	31m 56s
Build on Linux (python lighting-app)	10m 57s
Build on Darwin (clang, python_lib, simulated)	1h 9m 49s
Build on Linux (coverage)	16m 24s
	5h 36m 4s

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