subprojects/gvc: Bump gvc submodule to newest commit

A few fixes have landed in gvc recently that should fix a crash,
so bump the submodule to include those.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3233>

diff --git a/subprojects/gvc b/subprojects/gvc
index 000046e88714de77db320b0711af3baacb2813a2..91f3f41490666a526ed78af744507d7ee1134323 160000 (submodule)
--- a/subprojects/gvc
+++ b/subprojects/gvc
@@ -1 +1 @@
-Subproject commit 000046e88714de77db320b0711af3baacb2813a2
+Subproject commit 91f3f41490666a526ed78af744507d7ee1134323