I'm not a fan of people automatically saying sorry after a team kill. It takes the actual feel out of saying sorry. You can however bind a key to make it easier for you to activate the sorry voicecom however:
You don't have to bind it to your f key, pick your favorite.
[SELECT ALL] Code:
/bind f [ voicecom sorry "sorry" ]
You don't have to bind it to your f key, pick your favorite.