Add SPDX header

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/src/main/res/values/bools.xml

@@ -1,11 +1,11 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!--
+<?xml version="1.0" encoding="utf-8"?> -
+<!-- -
   ~ Nextcloud - Android Client
   ~
   ~ SPDX-FileCopyrightText: 2021-2024 Nextcloud GmbH and Nextcloud contributors
   ~ SPDX-FileCopyrightText: 2021 Tobias Kaminsky <tobias@kaminsky.me>
   ~ SPDX-License-Identifier: AGPL-3.0-or-later
--->
-<resources>
+--> -
+<resources> -
     <bool name="show_push_warning">true</bool>
-</resources>
+</resources> -