IDLE calltips currently contain "  # '/' marks preceding args as positional-only." when the signature contains '/' because, before 3.8, '/' was only used by argument clinic and only displayed by inspect.signature.  Now that '/' is a regular part of Python, the special note is not needed for the 3.8+ versions of IDLE.

The get_argspec docstring also needs updating, and I think the body has some redundant code.  The main test change needed is to remove the '/' note from expected returns.  I may first isolate any affected tests to minimize the difference between 3.7 and 3.8-9 code, so as to minimize the possibility of merge conflicts in backports.