Use monochrome symbolic icon for edit as new action
Summary: All other icons in the context menu are monochrome, so this one should too to be consistent
Test Plan:
Reviewers: KDE PIM: KMail, vkrause
Reviewed By: vkrause
Subscribers: vkrause, kde-pim
Tags: KDE PIM
Differential Revision: https://phabricator.kde.org/D26380