Convert files to SPDX that the automatic conversion missed

akonadi-mime.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <!--
-It comes with ABSOLUTELY NO WARRANTY, to the extent permitted by law. You may
-redistribute copies of update-mime-database under the terms of the GNU General
-Public License. For more information about these matters, see the file named
-COPYING.
+SPDX-License-Identifier: GPL-2.0-or-later
 -->
 <!--
 Notes:

src/xml/autotests/collectiontest.cpp

 /*
-    Copyright (c) Igor Trindade Oliveira <igor_trindade@yahoo.com.br>
+    SPDX-FileCopyrightText: Igor Trindade Oliveira <igor_trindade@yahoo.com.br>
 
     SPDX-License-Identifier: LGPL-2.0-or-later
 */