Remove copy code path

[robmikh]

Due to a bug in build 17763, buffers from the capture API cannot be directly handed to the Transcoding API. There's currently a workaround to copy the buffer, but I don't think it's correctly synchronized. When the next release ships, remove the workaround and bump the minimum required build.

[robmikh]

Alternative: In light of #6, it may make more sense to have the copy code path be triggered by either being on build 17763 or if the content size of the frame doesn't match the buffer size.