IONOS(gdata): add submodule at v31.2.1

Signed-off-by: Kai Henseler <kai.henseler@strato.de>

Author: bromiesTM

.gitmodules

@@ -91,3 +91,6 @@
 [submodule "apps-external/ncw_tools"]
 	path = apps-external/ncw_tools
 	url = git@github.com:IONOS-Productivity/ncw-tools.git
+[submodule "apps-external/gdatavaas"]
+	path = apps-external/gdatavaas
+	url = git@github.com:GDATASoftwareAG/nextcloud-gdata-antivirus.git