[kio-extras] Use "storage media" instead of "storages"
Summary: This patch improves the label's grammar.
Reviewers: VDG, ngraham
Reviewed By: VDG, ngraham
Subscribers: kde-frameworks-devel, kfm-devel
Tags: Dolphin, Frameworks
Differential Revision: https://phabricator.kde.org/D19053