Bump external/bpf_conformance from `4723912` to `90b453f` #1524

Job	Run time
build_ubuntu (Debug, tests)	21m 1s
build_windows (Debug, tests)	39m 55s
build_ubuntu (Debug, library)	1m 8s
build_windows (Debug, library)	3m 41s
build_ubuntu (Release, tests)	5m 53s
build_windows (Release, tests)	11m 27s
build_ubuntu (Release, library)	1m 5s
build_windows (Release, library)	5m 15s
	1h 29m 25s

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