Bump holochain_p2p from 0.2.3-beta-rc.0 to 0.3.0-beta-dev.18

Bumps [holochain_p2p](https://github.com/holochain/holochain) from 0.2.3-beta-rc.0 to 0.3.0-beta-dev.18.
- [Release notes](https://github.com/holochain/holochain/releases)
- [Changelog](https://github.com/holochain/holochain/blob/develop/CHANGELOG.md)
- [Commits](holochain/holochain@holochain_p2p-0.2.3-beta-rc.0...holochain_p2p-0.3.0-beta-dev.18)

---
updated-dependencies:
- dependency-name: holochain_p2p
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>