Bump swiftmailer/swiftmailer to 6.3.0

Signed-off-by: Côme Chilliet <come.chilliet@nextcloud.com>

diff --git a/3rdparty b/3rdparty
index c1fe9577fcc7006273d35848598df01eaa708b4f..02ba5bba999b61d40c79a6ed56683b69edf66619 160000 (submodule)
--- a/3rdparty
+++ b/3rdparty
@@ -1 +1 @@
-Subproject commit c1fe9577fcc7006273d35848598df01eaa708b4f
+Subproject commit 02ba5bba999b61d40c79a6ed56683b69edf66619