[Snyk] Security upgrade alpine from latest to 3.15.3#3

snyk-bot wants to merge 1 commit intomasterwardialer/lightning-network:masterfrom

snyk-fix-da1a8cb0664d1d4abff78d9fdd1caebcwardialer/lightning-network:snyk-fix-da1a8cb0664d1d4abff78d9fdd1caebcCopy head branch name to clipboard