Unused, undocumented argument assume_missing_is_default in check_handler_compatibility

[mattwthompson]

Is your feature request related to a problem? Please describe.

openff-toolkit/openff/toolkit/typing/engines/smirnoff/parameters.py

Line 3201 in b739698

self, other_handler, assume_missing_is_default=True

openff-toolkit/openff/toolkit/typing/engines/smirnoff/parameters.py

Line 3268 in b739698

self, other_handler, assume_missing_is_default=True

Describe the solution you'd like

Remove these since they do nothing but confuse me and any user who tries to understand what they do

Describe alternatives you've considered

Additional context

In this PR, this argument was removed from several other methods of the same name, but not these two: ea4231f

This is an "API break" except it currently does nothing and should not exist