build: release Lotus node and miner v1.30.0-rc2

[rjan90]

Related Issues

#12480

Proposed Changes

Bump version to v1.30.0-rc2 and prep the changelog for v1.30.0-rc2.

Checklist

Before you mark the PR ready for review, please make sure that:

• Commits have a clear commit message.
• PR title conforms with contribution conventions
• Update CHANGELOG.md or signal that this change does not need it per contribution conventions
• New features have usage guidelines and / or documentation updates in
  • Lotus Documentation
  • Discussion Tutorials
• Tests exist for new functionality or change in behavior
• CI is green

[rjan90]

Releases in draft here:

• https://github.com/filecoin-project/lotus/releases/tag/untagged-a1bc7a38a1916346c74f
• https://github.com/filecoin-project/lotus/releases/tag/untagged-1dc35c80de528b4eb457