Update version to 13.0.0-rc1

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
diff --git a/VERSION b/VERSION
index 9637d43..0ee82ac 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-12.1.0-devel
+13.0.0-rc1