pallet-bounties: allow bounties to never expire #23633

Job	Run time
isdraft / isdraft	1s
check-dependency-rules	9s
check-fail-ci	9s
check-markdown	16s
check-workspace	18s
check-readme	3m 28s
preflight / preflight	9s
preflight / ci-versions	1m 23s
check-rust-feature-propagation	2m 27s
fmt	1m 32s
check-toml-format	1m 8s
test-rust-features	2m 7s
check-umbrella	2m 12s
All quick checks passed	1s
	15m 20s

Provide feedback