package/gnuplot: security bump to version 5.4.1

- Fix CVE-2020-25412: com_line() in command.c in gnuplot 5.4 leads to an
  out-of-bounds-write from strncpy() that may lead to arbitrary code
  execution.
- Drop second patch (already in version)
- Update indentation in hash file (two spaces)

http://gnuplot.info/ReleaseNotes_5_4_1.html



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>