Bump VERSION to v1.12.1

Signed-off-by: Tibor Vass <tibor@docker.com>
diff --git a/VERSION b/VERSION
index c2cbf3e..f8f4f03 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.12.1-rc2
+1.12.1