accounts-db: get rid of const in tests #5927

Job	Run time
cargo-test-sbf (token/program)	9m 8s
cargo-test-sbf (instruction-padding/program, token/program-2022, token/program-2022-test)	15m 55s
cargo-test-sbf (associated-token-account/program, associated-token-account/program-test)	10m 29s
cargo-test-sbf (token-upgrade/program)	10m 26s
check	4m 9s
cargo-test-sbf (feature-proposal/program)	9m 57s
test (token/cli, token/program, token/program-2022, associated-token-account/program, instruction...	21m 11s
test (single-pool/cli, single-pool/program)	21m 22s
cargo-test-sbf (governance/addin-mock/program, governance/program)	12m 54s
test (token-upgrade/cli, token-upgrade/program)	18m 27s
cargo-test-sbf (memo/program)	9m 19s
cargo-test-sbf (name-service/program)	9m 13s
cargo-test-sbf (stake-pool/program)	15m 8s
cargo-test-sbf (single-pool/program)	9m 58s
	2h 57m 36s

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