[libcalamares] Remove empty .cpp file

- Requirement.cpp was there "just in case" the header grew
  functions that need an implementation, but that seems
  unlikely (the header is just a struct of POD).

src/libcalamares/CMakeLists.txt

@@ -62,7 +62,6 @@ set( libSources
     # Modules
     modulesystem/InstanceKey.cpp
     modulesystem/Module.cpp
-    modulesystem/Requirement.cpp
     modulesystem/RequirementsChecker.cpp
     modulesystem/RequirementsModel.cpp
 

src/libcalamares/modulesystem/Requirement.cpp

@@ -1,22 +0,0 @@
-/* === This file is part of Calamares - <https://github.com/calamares> ===
- * 
- *   SPDX-FileCopyrightText: 2017 Adriaan de Groot <groot@kde.org>
- *
- *   Calamares is free software: you can redistribute it and/or modify
- *   it under the terms of the GNU General Public License as published by
- *   the Free Software Foundation, either version 3 of the License, or
- *   (at your option) any later version.
- *
- *   Calamares is distributed in the hope that it will be useful,
- *   but WITHOUT ANY WARRANTY; without even the implied warranty of
- *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- *   GNU General Public License for more details.
- *
- *   You should have received a copy of the GNU General Public License
- *   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
- *
- *   SPDX-License-Identifier: GPL-3.0-or-later
- *   License-Filename: LICENSE
- *
- */
-#include "Requirement.h"