Flaky tests

### Describe the bug

There are some flaky tests needed be fixed.

- [x] [test/unit/utils/clock.test.ts > util / Clock > getCurrentSlot > 'should return next slot after 11.5s'](https://github.com/ChainSafe/lodestar/actions/runs/7652507863/job/20852823580#step:6:714)
- [x] [test/e2e/network/gossipsub.test.ts > gossipsub / worker > Publish and receive a blsToExecutionChange](https://github.com/ChainSafe/lodestar/actions/runs/7652507863/job/20852770547#step:6:3890)
- [ ] [test/e2e/api/impl/lightclient/endpoint.test.ts > lightclient api > getOptimisticUpdate()](https://github.com/ChainSafe/lodestar/actions/runs/7855861634/job/21438200871?pr=6417#step:6:4190)
- [x] [test/e2e/network/reqresp.test.ts > network / reqresp / worker > Sleep infinite on first byte](https://github.com/ChainSafe/lodestar/actions/runs/7671034884/job/20908688781#step:6:3946)
- [x] [test/e2e/network/reqresp.test.ts > network / reqresp / worker > Sleep infinite on second response chunk](https://github.com/ChainSafe/lodestar/actions/runs/7671034884/job/20908688781#step:6:3960)
- [ ] [test/e2e/sync/unknownBlockSync.test.ts > sync / unknown block sync > should do an unknown block parent sync from another BN](https://github.com/ChainSafe/lodestar/actions/runs/7671034884/job/20908688781#step:6:3914)
- [x] [test/e2e/network/gossipsub.test.ts > gossipsub / worker > Publish and receive a voluntaryExit](https://github.com/ChainSafe/lodestar/actions/runs/7687085125/job/20946738011?pr=6363#step:6:3964)
- [x] [ test/e2e/network/gossipsub.test.ts > gossipsub / worker > Publish and receive a LightClientFinalityUpdate](https://github.com/ChainSafe/lodestar/actions/runs/7687085125/job/20946738011?pr=6363#step:6:3965)
- [ ] [test/e2e/sync/unknownBlockSync.test.ts > sync / unknown block sync > should do an unknown block parent sync from another BN](https://github.com/ChainSafe/lodestar/actions/runs/7687085125/job/20946738011?pr=6363#step:6:3981)
- [x] [test/e2e/network/reqresp.test.ts > network / reqresp / worker > trigger a RESP_TIMEOUT error](https://github.com/ChainSafe/lodestar/actions/runs/7687451427/job/20947518693#step:6:3927)
- [x] [test/e2e/network/reqresp.test.ts > network / reqresp / worker > should send/receive a light client update message](https://github.com/ChainSafe/lodestar/actions/runs/7628049759/job/20778285481?pr=6344#step:6:219)
- [x] [test/unit/beacon/genericServerTest/config.test.ts > beacon / config > Run generic server test](https://github.com/ChainSafe/lodestar/actions/runs/7698507615/job/20978169368?pr=6241#step:6:497)
- [x] Few E2E test failing with `Error: Too many messages for missing streams) not instanceof LodestarError: Error: Too many messages for missing streams` Related to https://github.com/libp2p/js-libp2p/pull/2387
- [ ] [Error: Couldn't find a matching chrome browser for tag "123.0.6290.0" on platform "linux"](https://github.com/ChainSafe/lodestar/actions/runs/7847020467/job/21416404814?pr=6415#step:7:70)
- [ ] [test/unit/sanityCheck.test.ts](https://github.com/ChainSafe/lodestar/actions/runs/14709617547/job/41278936158?pr=7665#step:5:1652)
- [x] [AxiosError: Request failed with status code 429](https://github.com/ChainSafe/lodestar/actions/runs/14731164867/job/41349996153?pr=7762#step:6:10755)

### Expected behavior

All tests should behave as stable they could.

### Steps to reproduce

- Run all tests

### Additional context

During CI runs on different PRs we found few

### Operating system

Linux

### Lodestar version or commit hash

unstable