Update screenshots for Calligra sheets 3.1

Summary: Update screenshots for Calligra sheets 3.1 also reflect change in a menu name. Only the hidencells screenshots aren't updated. I wasn't able to reproduce the steps.

Test Plan: checkXML5 index.dockbook

Reviewers: #calligra:_3.0, #documentation, yurchor

Reviewed By: #documentation, yurchor

Subscribers: yurchor, leinir, Calligra-Devel-list, kde-doc-english

Tags: #calligra:_3.0, #documentation

Differential Revision: https://phabricator.kde.org/D18994