Update the compat version with ControlSystems

[albheim]

Seems to be some testing errors from using it with ControlSystems 0.9, but otherwise it seemed to work fine for some small manual tasks I had.

[baggepinnen]

It seems that some of the test failures are due to a change in sympy not yet taken care of by SymPy.jl

PyError ($(Expr(:escape, :(ccall(#= /home/fredrikb/.julia/packages/PyCall/tqyST/src/pyfncall.jl:43 =# @pysym(:PyObject_Call), PyPtr, (PyPtr, PyPtr, PyPtr), o, pyargsptr, kw))))) <class 'TypeError'>
  TypeError("replace() got an unexpected keyword argument 'simultaneous'")
    File "/home/fredrikb/.local/lib/python3.8/site-packages/sympy/simplify/simplify.py", line 573, in simplify
      expr = expr.replace(