ProjectImportJob killing causes deadlocks/crashes.

Until it works properly, don't make it killable.
BUG: 256709

project/importprojectjob.cpp

@@ -63,8 +63,6 @@ public:
 ImportProjectJob::ImportProjectJob(ProjectFolderItem *folder, IProjectFileManager *importer)
     : KJob(0), d(new ImportProjectJobPrivate )
 {
-    setCapabilities(Killable);
-    
     d->m_importer = importer;
     d->m_folder = folder;
     d->m_project = folder->project();