Remove FrontSide audio when type answer feature is used.

This is a rather benign code change. Previously, code attempted to strip the entire part introduced by {{FrontSide}}, but as pointed out by Xiao, type answer prompts broke this since the FrontSide content is altered so as not be literally found. This changes the code to only look for exactly the embedded sounds from FrontSide. It has been testing to work with type answer prompts.

I'm not sure if develop is the right branch to push to for code changes that are appropriate for the upcoming/current beta, but this fix would be a fine thing to include there, and it is my intention that it be included there.