Removes unused member variables

Summary: The InformationPanel::m_pendingPreview and ApplyViewPropsJob::m_currentItem member variables are not used and can therefore be removed.

Reviewers: broulik, elvisangelaccio

Reviewed By: broulik, elvisangelaccio

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D14180