Suspended unit test

this was found on MacOS where verifyMultipleAggregateSignatures.test.ts is suspended

```
test/unit/aggregateWithRandomness.test.ts:
✓ Aggregate With Randomness > aggregateWithRandomness() > should not accept an empty array argument [0.02ms]
» Aggregate With Randomness > aggregateWithRandomness() > should accept an array of {pk: PublicKey, sig: Uint8Array}
✓ Aggregate With Randomness > aggregateWithRandomness() > should throw for invalid serialized [0.60ms]
✓ Aggregate With Randomness > aggregateWithRandomness() > should return a {pk: PublicKey, sig: Signature} object [0.91ms]
✓ Aggregate With Randomness > aggregateWithRandomness() > should add randomness to aggregated publicKey [0.79ms]
✓ Aggregate With Randomness > aggregateWithRandomness() > should add randomness to aggregated signature [0.66ms]
✓ Aggregate With Randomness > aggregateWithRandomness() > should produce verifiable set [2.13ms]
✓ Aggregate With Randomness > aggregateWithRandomness() > should not validate for different message [1.80ms]
✓ Aggregate With Randomness > aggregateWithRandomness() > should not validate included key/sig for different message [1.64ms]
✓ Aggregate With Randomness > aggregateWithRandomness() > should return different signatures for different sets [1.72ms]
✓ Aggregate With Randomness > aggregateWithRandomness() > should return different signatures for different times [1.54ms]
✓ Aggregate With Randomness > asyncAggregateWithRandomness() > should not accept an empty array argument [0.09ms]
✓ Aggregate With Randomness > asyncAggregateWithRandomness() > should throw for invalid serialized [2.39ms]
✓ Aggregate With Randomness > asyncAggregateWithRandomness() > should return a {pk: PublicKey, sig: Signature} object [2.48ms]
✓ Aggregate With Randomness > asyncAggregateWithRandomness() > should add randomness to aggregated publicKey [2.28ms]
✓ Aggregate With Randomness > asyncAggregateWithRandomness() > should add randomness to aggregated signature [2.40ms]
✓ Aggregate With Randomness > asyncAggregateWithRandomness() > should produce verifiable set [3.28ms]
✓ Aggregate With Randomness > asyncAggregateWithRandomness() > should not validate for different message [3.04ms]
✓ Aggregate With Randomness > asyncAggregateWithRandomness() > should not validate included key/sig for different message [3.23ms]

test/unit/verifyMultipleAggregateSignatures.test.ts:
```

this happens even before we implement thread pool in blst-z https://github.com/ChainSafe/blst-z/pull/28