Remove TryFrom for ComItf
Remove TryFrom for ComItf

This was invalid for the current compiler even before it landed in the
repository. Rust made the coherence rules stricter, which prevents generic
implementation of TryFrom thanks to the implicit implementation through
the From trait.

Rantanen/com-export-rs,Rantanen/com-export-rs,Rantanen/com-export-rs,Rantanen/com-export-rs