This fixes an issue I ran into in UI Automation using an interface proxy marshaled with `MSHCTX_INPROC`. `CoUnmarshalInterface` always passes `MSHCTX_LOCAL` when the standard marshaler, regardless of what was passed to `CoMarshalInterface`.
When passing an interface that uses the free threaded marshaler as an argument to a method on the proxy retrieved from `CoUnmarshalInterface`, it passes `MSHCTX_LOCAL` when trying to marshal, which the results in the free threaded marshaler trying to create a proxy/stub which fails.