Release v4.2.0-beta.1

What's Changed

• v4.2: runtime: Feature gate burning epoch reward sysvar lamports (backport of #13611) by @mergify[bot] in #13643
• v4.2: Gossip purge duration (backport of #13668) by @mergify[bot] in #13680
• v4.2: fix(runtime): Avoid panicking if stake_rewards capacity turns out be larger (backport of #13697) by @mergify[bot] in #13706

Full Changelog: v4.2.0-beta.0...v4.2.0-beta.1