releases: Remove versions.yaml

The milestone check reads the next versions from the pinned branch
status issue now, and nothing else uses this file.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

releases/versions.yaml

@@ -1,4 +0,0 @@
----
-docker:
-  last: "29.9.1"
-  next: "29.10.0"