doc: remove the SPDX header from a documentation string

This is a user-visible message in the documentation.

doc/kcontrol/plasma-pa/index.docbook

@@ -105,7 +105,7 @@ Configuration: This tab allows to set specific profiles to such as Analog Stereo
 &i18n-plasmapa;
 </para>
 <para>
-Program SPDX-FileCopyrightText: 2014-2015 Harald Sitter
+Program copyright 2014-2015 Harald Sitter
 </para>
 
 <para>