remove fixation for matplotlib

[Reimar Bauer]

in #397 we recognized a problem in matplotlib 3.1.0, we have to recheck or to fix it upstream

[Joern Ungermann]

matplotlib 3.1.2+3.1.3 work.

[Joern Ungermann]

I have troubles getting it to install matplotlib 3.2

I would suggest removing the fix to the old matplotlib version and see what happens :-)

[Reimar Bauer]

fixation removed by

https://bitbucket.org/wxmetvis/mss/pull-requests/875/changed-fixations-of-some-modules-fixes