maint: Update to latest gnulib

This pulls in, among other new things, vc-list-files fix to make
syntax-check work with git worktrees.

Signed-off-by: Erik Skultety <eskultet@redhat.com>

diff --git a/.gnulib b/.gnulib
index ce4ee4cbb596a9d7de2786cf8c48cf62a4edede7..8d116e3f657cb120f79efbbb675fa3cc9d21f53e 160000 (submodule)
--- a/.gnulib
+++ b/.gnulib
@@ -1 +1 @@
-Subproject commit ce4ee4cbb596a9d7de2786cf8c48cf62a4edede7
+Subproject commit 8d116e3f657cb120f79efbbb675fa3cc9d21f53e