pallet-bounties: allow bounties to never expire #23634

Job	Run time
isdraft / isdraft	1s
check-dependency-rules	8s
check-workspace	22s
check-fail-ci	15s
check-markdown	13s
check-readme	3m 11s
preflight / preflight	6s
preflight / ci-versions	1m 7s
check-rust-feature-propagation	2m 5s
check-toml-format	1m 10s
fmt	1m 17s
check-umbrella	2m 26s
test-rust-features	2m 12s
All quick checks passed	1s
	14m 34s

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