[libcalamares] Don't double-include FileSystem

The partitioning header 'FileSystem.h' is for KPMCore support;
it is already included by Global.h and guarded by ifdefs for
KPMCore. Do not unconditionally include it from the implementation.

src/libcalamares/partition/Global.cpp

@@ -9,7 +9,6 @@
  */
 #include "Global.h"
 
-#include "FileSystem.h"
 #include "GlobalStorage.h"
 #include "JobQueue.h"