Switch to latest core in order to fix auth-groupe-x administration, again.

Signed-off-by: Raphaël Barrois <raphael.barrois@polytechnique.org>

diff --git a/core b/core
index c16eff5..f9489e4 160000 (submodule)
--- a/core
+++ b/core
@@ -1 +1 @@
-Subproject commit c16eff5c3e6530afbb394a8c971dd5813a6f955d
+Subproject commit f9489e456f03733d9d7babc8ab367251b4272792