chore: add a witness for `enum_variant_missing` #2939

Job	Run time
Build binary	39s
Build binary (Windows)	2m 37s
Check lint and rustfmt	28s
Run tests (1.77, false)	2m 36s
Run tests (1.78, false)	2m 52s
Semver: core-graphics	46s
Check if version changed	20s
Run tests (1.79, false)	2m 26s
Run tests (1.80, false)	2m 25s
Run tests (1.81, false)	2m 17s
Run tests (stable, false)	1m 8s
Run tests (beta, false)	2m 7s
Run tests (nightly, true)	2m 5s
Semver: libp2p-dcutr 1.62.0 and libp2p-relay 0.14.0	1m 16s
Semver: libp2p-core 0.37.0	55s
Caching across rustdoc versions	1m 24s
Caching with feature config changed	26s
Semver: bevy_core v0.9.0	37s
Semver: bevy_gltf v0.9.1	1m 0s
Semver: libp2p-gossipsub ~0.44.0 + libp2p-request-response ~0.24.0	1m 12s
Semver: clap v3.2.0	44s
Semver: libp2p-uds 0.37.0	1m 13s
Semver: tokio ~v1.25.0 (explicit)	4s
Semver: sqllogictest v0.13.0	41s
Semver: tokio ~v1.25.0 (implicit)	7s
Semver: dependency has warnings with "-Dwarnings" (libp2p v0.53.1)	1m 6s
Check failure when installed rustc is too old	17s
Semver: perf-event-open-sys2 v5.0.0	32s
Semver: ref-slice fork (git)	26s
Semver: ref-slice fork (sparse)	19s
Semver: ref-slice fork (Windows) (git)	58s
Semver: ref-slice fork (Windows) (sparse)	49s
All CI stages	1s
Check for semver compliance	0s
Run the release workflow	0s
	36m 53s

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