correct vscode icon name
Summary: com.visualstudio.code.svg and com.visualstudio.code.oss.svg
Reviewers: Breeze, cblack, VDG, ndavis, ngraham
Reviewed By: Breeze, VDG, ngraham
Subscribers: ngraham, kde-frameworks-devel
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D29083