misc: update copyright date

accountitemdelegate.cpp

accountitemdelegate.h

accountlistmodel.cpp

accountlistmodel.h

advancedsettingswidget.cpp

advancedsettingswidget.h

animationhelpers.cpp

animationhelpers.h

avatargraphicsview.cpp

avatargraphicsview.h

bannedlistmodel.cpp

bannedlistmodel.h

callwidget.cpp

callwidget.h

conversationsfilterwidget.cpp

conversationsfilterwidget.h

currentaccountcombobox.cpp

currentaccountcombobox.h

deleteaccountdialog.cpp

deleteaccountdialog.h