Fixup module docstring in sim.py
Fixup module docstring in sim.py

The copyright notice should surely be in a comment, rather than the
docstring. And change the docstring itself to match what the file
does.

lowRISC/ibex,AmbiML/ibex,lowRISC/ibex,AmbiML/ibex,lowRISC/ibex,AmbiML/ibex,AmbiML/ibex,lowRISC/ibex