Bump solc from 0.8.7-fixed to 0.8.28 in /solidity #2149

Job	Run time
check	2m 36s
rustfmt	7s
clippy	27s
integration-test-althea-payment	15m 38s
integration-test-eth-payments	15m 51s
audit	14s
integration-test-debts	15m 39s
integration-test-five-nodes	11m 6s
integration-test-multi-exit	12m 43s
test	5m 28s
integration-test-db-migration	10m 40s
integration-test-validate-contract	10m 17s
cross-armv7	1m 7s
cross-aarch64	4m 37s
	1h 46m 30s

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