[3rdparty] Bump symfony to 4.2.8

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

diff --git a/3rdparty b/3rdparty
index bbef51b59e027569b9eebf0805342fcb2568848e..ef289bc27eae0cdfc3f74f419ace8dda8dd84ef0 160000 (submodule)
--- a/3rdparty
+++ b/3rdparty
@@ -1 +1 @@
-Subproject commit bbef51b59e027569b9eebf0805342fcb2568848e
+Subproject commit ef289bc27eae0cdfc3f74f419ace8dda8dd84ef0