[Kst] [Kst-plot/kst] f68953: add missing tr() call

[Burkhard Lück]

  Branch: refs/heads/master
  Home:   https://github.com/Kst-plot/kst
  Commit: f689536cef591f9d21ea8f76162fb6ebea474f24
      https://github.com/Kst-plot/kst/commit/f689536cef591f9d21ea8f76162fb6ebea474f24
  Author: Burkhard Lück <lueck at hube-lueck.de>
  Date:   2014-01-16 (Thu, 16 Jan 2014)

  Changed paths:
    M src/libkstapp/mainwindow.cpp

  Log Message:
  -----------
  add missing tr() call