Bump external/bpf_conformance from `b544539` to `514fa97` #159

Job	Run time
build_ubuntu (Debug, tests)	33m 47s
build_windows (Debug, tests)	43m 48s
build_ubuntu (Debug, library)	1m 11s
build_ubuntu (Release, tests)	6m 13s
build_windows (Debug, library)	4m 14s
build_windows (Release, tests)	10m 4s
build_ubuntu (Release, library)	1m 14s
build_windows (Release, library)	6m 12s
	1h 46m 43s

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