Add `unstable-api` feature flag to `pallet-revive` #16319

Job	Run time
check-dependency-rules	7s
check-markdown	13s
check-workspace	18s
check-fail-ci	13s
check-readme	3m 1s
preflight / preflight	44s
preflight / ci-versions	1m 0s
fmt	1m 14s
check-toml-format	1m 4s
check-rust-feature-propagation	2m 5s
check-umbrella	2m 25s
test-rust-features	2m 4s
All quick checks passed	1s
	14m 29s

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