Bump FIRST_VERSION_REQUIRED_FOR_PROTOCOL_20 #4725

Job	Run time
cackle	2m 0s
fmt	12s
cargo-deny (advisories)	51s
build (gcc, current)	1h 0m 41s
rust-check-git-rev-deps	15s
cargo-deny (bans licenses sources)	47s
build (gcc, current, --check-test-tx-meta)	55m 11s
build (gcc, next)	56m 31s
build (gcc, next, --check-test-tx-meta)	57m 48s
build (clang, current)	53m 25s
build (clang, current, --check-test-tx-meta)	45m 50s
build (clang, next)	53m 35s
build (clang, next, --check-test-tx-meta)	46m 30s
complete	1s
	7h 13m 37s

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