Remove ownCloud 10.5 upgrade path

Signed-off-by: Vincent Petry <vincent@nextcloud.com>

version.php

@@ -41,7 +41,6 @@ $OC_VersionCanBeUpgradedFrom = [
 		'26.0' => true,
 	],
 	'owncloud' => [
-		'10.5' => true,
 		'10.11' => true,
 	],
 ];