* gnu/packages/kde-plasma.scm (system-settings): Update to 6.1.2. [inputs]: Remove kactivities, kactivities-stats, qtdeclarative-5, qtquickcontrols-5, qtquickcontrols2-5, kirigami-addons, qtgraphicaleffects, kdeclarative, kuserfeedback, knewstuff, plasma-pa, bluez-qt, kwin, and bluedevil; add plasma-activities, plasma-activities-stats, and qtdeclarative. [arguments]: Set #:qtbase to qtbase. Change-Id: I9c6a993e1a051e54ea01d228aa5923b782aae113