Chart: Remove unused frame/background stuff from legend
Summary:
Remove setter/getters and ui.
These things are controlled from the Shape Tool,
so the KChart things shall not be used.
Reviewers: #calligra:_3.0, leinir, mecir, boemann
Reviewed By: leinir
Tags: #calligra:_3.0
Differential Revision: https://phabricator.kde.org/D12169