#16 Ensure desktop file is closed after reading

[Chris Mayo]

/usr/lib/python3.8/site-packages/Prophet/Desktop/__init__.py:184:
    ResourceWarning: unclosed file <_io.BufferedReader name='/usr/share/applications/gcm-calibrate.desktop'>
  xs = codecs.open(desktop, "r", "utf-8").readlines()  # Py 2.4+