Move default value for --rpc-pubsub-notification-threads to CLI #500

Job	Run time
cargo-test-sbf (token/program)	7m 8s
cargo-test-sbf (instruction-padding/program, token/program-2022, token/program-2022-test)	11m 10s
check	0s
cargo-test-sbf (associated-token-account/program, associated-token-account/program-test)	10m 57s
cargo-test-sbf (token-upgrade/program)	7m 25s
test	0s
cargo-test-sbf (feature-proposal/program)	8m 19s
cargo-test-sbf (governance/addin-mock/program, governance/program)	14m 5s
cargo-test-sbf (memo/program)	7m 13s
cargo-test-sbf (name-service/program)	7m 57s
cargo-test-sbf (stake-pool/program)	10m 29s
cargo-test-sbf (single-pool/program)	8m 2s
	1h 32m 45s

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