Drop pydot2 and pydotplus in favor of modern pydot

[matthewfeickert]

Both pydot2 and pydotplus haven't had releases until 2014 and should be considered abandoned and dropped from use. pydot is still developed.

The only use of pydotplus in the yadage org is in yadage's visualize module:

yadage/yadage/visualize.py

Line 6 in cbb2651

import pydotplus

Related Issues:

• Issue upgrade pydot2 to be forward-setuptools-friendly #105 (thanks @tiborsimko for this!)
• Try to remove or replace pydotplus adage#24
• setup: upgrading to adage==0.10.2 breaks yadage workflows reanahub/reana-workflow-engine-yadage#220
• ci: Add CI using GitHub Actions workflows  adage#17 (comment)

[matthewfeickert]

I now realize this is basically a duplicate of Issue #105. Woops. I'll keep this open as it is easy for me to find, but the resulting PR can close both.