Release 2.15.6

What's Changed

• Pre-pull solution images on the kind nodes before deploying Zenko by @delthas in #2474
• MongoDbPodRecovering alert firing once per reporting pod instead of once per recovering member by @benzekrimaha in #2471
• Remove VERSION file by @francoisferrand in #2513
• 🐛(ZENKO-5346) remove duplicated word in ConsumerLagWarning description by @DarkIsDude in #2492
• Fix releasing workflow by @francoisferrand in #2520
• Bump vault with signatureAge of 0 fix by @benzekrimaha in #2493
• Use OpenJDK-based zookeeper image & release by @francoisferrand in #2541

Full Changelog: 2.15.5...2.15.6