Bump node from 20.8.0-buster-slim to 20.12.2-buster-slim in /docker/backend#435

dependabot[bot] wants to merge 1 commit intomasterhunicus/mempool:masterfrom

dependabot/docker/docker/backend/node-20.12.2-buster-slimhunicus/mempool:dependabot/docker/docker/backend/node-20.12.2-buster-slimCopy head branch name to clipboard