util/tracing: switch to semconv v0.21.0 #4675

Job	Run time
prepare	1s
test / prepare	1m 57s
test / run (containerd, ./frontend/dockerfile, integration)	4m 49s
test / run (containerd, ./frontend/dockerfile, dockerfile)	6m 42s
test / run (containerd-rootless, ./frontend/dockerfile, integration)	4m 46s
test / run (containerd-rootless, ./frontend/dockerfile, dockerfile)	6m 43s
test / run (containerd-1.6, ./frontend/dockerfile, integration)	4m 42s
test / run (containerd-1.6, ./frontend/dockerfile, dockerfile)	6m 55s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, integration)	5m 19s
test / run (containerd-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	7m 10s
test / run (oci, ./frontend/dockerfile, integration)	4m 36s
test / run (oci, ./frontend/dockerfile, dockerfile)	6m 42s
test / run (oci-rootless, ./frontend/dockerfile, integration)	4m 17s
test / run (oci-rootless, ./frontend/dockerfile, dockerfile)	5m 56s
test / run (oci-rootless-slirp4netns-detachnetns, ./frontend/dockerfile, integration)	4m 48s
test / run (oci-rootless-slirp4netns-detachnetns, ./frontend/dockerfile, dockerfile)	5m 38s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, integration)	4m 50s
test / run (oci-snapshotter-stargz, ./frontend/dockerfile, dockerfile)	6m 44s
image (mainline)	4m 53s
image (labs)	4m 53s
scout	0s
release	0s
	1h 42m 21s

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