Replace python 2 code using pychart to draw a graph in
osmux-reference.adoc with the generated svg file. The upstream of
pychart is dead, there is no python 3 version, and python 2 is EOL at
the end of 2019.
This is the only time we ever made use of pychart in osmo-gsm-manuals,
so with this change, we can just drop the dependency.
I've generated the chart by saving the python code in chart.py, then:
$ ./chart.py --format=svg --font-size=3 > chart.svg
Related: OS#2819, OS#4193
Depends: osmo-ci I754b133d77743582bd84c33c74ecc9eb9ca4c0ef
Change-Id: I36b721f895caee9766528e14d854b6aa2a2fac85
Oliver Smith
f659f5e5b0