Bump symfony to 4.4.4

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

diff --git a/3rdparty b/3rdparty
index 97b5fa3e9364f21961edad6ed1315d48bc45bd80..7b4be1f0bf34c520e5672c8a6fb79de27191a93b 160000 (submodule)
--- a/3rdparty
+++ b/3rdparty
@@ -1 +1 @@
-Subproject commit 97b5fa3e9364f21961edad6ed1315d48bc45bd80
+Subproject commit 7b4be1f0bf34c520e5672c8a6fb79de27191a93b