multi: fix `staticcheck` flags #2821

Job	Run time
go mod check	9m 53s
run unit-test sqlite3 race	9m 30s
RPC compilation check	1m 32s
build and lint code	4m 52s
verify that auto-generated documentation is up-to-date	23s
run unit-test postgres race	10m 50s
SQL compilation check	10s
run LiT itests	3m 26s
run LiT unit tests	6m 36s
	47m 12s

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