Replace deprecated KConfigDialogManager::changedMap with property in the class definition
Summary:
KConfigDialogManager::changedMap is deprecated since KF 5.32. This commit mimics the replacement commit from Okteta:
https://cgit.kde.org/okteta.git/commit/?id=1ed966965b656bac22e1fe99e1b7ede00da68263
Test Plan: Compiles. It seems that Equation editor behavior does not change.
Reviewers: KDE Edu, aacid
Reviewed By: aacid
Subscribers: kossebau, aacid, kde-edu
Tags: KDE Edu
Differential Revision: https://phabricator.kde.org/D25078