chore: mergify - update stable branches

[skip ci]
diff --git a/.mergify.yml b/.mergify.yml
index c5f3d83..804b27d 100644
--- a/.mergify.yml
+++ b/.mergify.yml
@@ -15,6 +15,8 @@
         - or:
           - base=version-13
           - base=version-12
+          - base=version-14
+          - base=version-15
     actions:
       close:
       comment: