RTA: verify that no commercial license headers exits on the 5.15.3 LGPL source package

Verify that the commercial license header does not exist on files included into the opensource src package:

Commercial license header:

https://codereview.qt-project.org/gitweb?p=qt/qtqa.git;a=blob;f=tests/prebuild/license/templates/header.COMM;h=a2a31f3b6bceacf5e3b19b5699fa7d21f7ec704f;hb=refs/heads/master

--> so, this should not exist on the files:

8 ** $QT_BEGIN_LICENSE:COMM$
9 **
10 ** Commercial License Usage
11 ** Licensees holding valid commercial Qt licenses may use this file in
12 ** accordance with the commercial license agreement provided with the
13 ** Software or, alternatively, in accordance with the terms contained in
14 ** a written agreement between you and The Qt Company. For licensing terms
15 ** and conditions see https://www.qt.io/terms-conditions. For further
16 ** information use the contact form at https://www.qt.io/contact-us.
17 **
18 ** $QT_END_LICENSE$