Change the evaluate worksheet icon at worksheet entry from view-refresh to system-run

Summary: Currently the icon in worksheet entry is an icon for "refresh/update" something. The use of "run" icon is consistent with the action in Cantor window and it improves a bit the usability for run worksheet entries.

Reviewers: asemke, sirgienko

Reviewed By: asemke

Subscribers: kde-edu

Tags: #kde_edu, #cantor

Differential Revision: https://phabricator.kde.org/D15012