WT-16736 (#14315) migrated all disagg multi-node test/format tasks from test/evergreen_disagg.yml to test/evergreen.yml (mainline waterfall). WT-18204 (#14320) was stacked on a pre-migration tree and accidentally re-introduced the four format-stress-test-disagg-multi* anchors and their eight tasks into test/evergreen_disagg.yml, where they are now pure duplication of mainline coverage. Remove them from the wiredtiger-disagg project. The format-stress-test-disagg-snapshot task stays for now; moving it to mainline will be handled under a separate ticket.