Remove 'ipympl' from setup.py dependencies (#213)

I try to package `ctaplot` for Guix (it's one the last 3 missing packages to bring `magic-cta-pipe`) but `ipympl` is not in use by any *.py files, but listed as install requirements.

`ipympl` was remove in Guix rectally, see https://codeberg.org/guix/guix/issues/5366.

Author: Hellseher

setup.py

@@ -38,7 +38,6 @@ def get_property(prop, project):
         'jupyter',
         'ipywidgets',
         'pyyaml',
-        'ipympl',
         'tqdm',
     ],
     tests_require=['pytest'],