sessionrunner: Change text from "New Session" to "Switch User"

This is how we call it since ~2016.

Because of the string changes, it can not get cherry-picked to stable.

BUG: 431315

runners/sessions/sessionrunner.cpp

@@ -133,7 +133,7 @@ void SessionRunner::match(Plasma::RunnerContext &context)
         Plasma::QueryMatch match(this);
         match.setType(Plasma::QueryMatch::ExactMatch);
         match.setIconName(QStringLiteral("system-switch-user"));
-        match.setText(i18n("New Session"));
+        match.setText(i18n("Switch User"));
         matches << match;
     }