Bump num-bigint from 0.4.3 to 0.4.4 #19

Job	Run time
check	12m 53s
test (token/cli, token/program, token/program-2022, associated-token-account/program)	33m 38s
test (single-pool/cli, single-pool/program)	26m 18s
test (token-upgrade/cli, token-upgrade/program)	24m 45s
cargo-test-sbf (token/program)	27m 3s
cargo-test-sbf (instruction-padding/program, token/program-2022, token/program-2022-test)	51m 30s
cargo-test-sbf (associated-token-account/program, associated-token-account/program-test)	25m 13s
cargo-test-sbf (token-upgrade/program)	27m 49s
cargo-test-sbf (feature-proposal/program)	25m 57s
cargo-test-sbf (governance/addin-mock/program, governance/program)	55m 56s
cargo-test-sbf (memo/program)	25m 57s
cargo-test-sbf (name-service/program)	18m 15s
cargo-test-sbf (stake-pool/program)	38m 7s
cargo-test-sbf (single-pool/program)	23m 11s
	6h 56m 32s

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