refactor: Use SPDX in appinfo/infox.xml

Co-authored-by: Ferdinand Thiessen <opensource@fthiessen.de>
Signed-off-by: Carl Schwan <carl@carlschwan.eu>

Author: CarlSchwan

appinfo/info.xml

@@ -14,7 +14,7 @@ Folders can be configured from *Team folders* in the admin settings.
 After a folder is created, the admin can give access to the folder to one or more teams, control their write/sharing permissions and assign a quota for the folder.
 ]]></description>
 	<version>19.1.20</version>
-	<licence>agpl</licence>
+	<licence>AGPL-3.0-or-later</licence>
 	<author>Robin Appelman</author>
 	<namespace>GroupFolders</namespace>
 	<types>