Convert video from 24 fps to 25, shortening length (no frame duplication), keeping audio pitch
If your input stream has no B-pyramid i.e. B-frames used as references for other B-frames, and your ffmpeg build has librubberband linked then use the following commands:

#1 Extract video to raw stream

ffmpeg -i in.mkv -c copy in.h264


#2 Retime and process audio

ffmpeg -r 25 -i in.h264 -i in.mkv -map 0 -map 1:a -af rubberband=tempo=1.04166 -c:a pcm_s16le out.mkv


If your H264 stream does have reference B-frames then you'll have to use mp4box as an intermediary.

i.e. 

#2a Retime video

mp4box -add in.h264#fps=25 -new in25.mp4


#2b Process audio and add video

ffmpeg -i in25.mp4 -i in.mkv -map 0 -map 1:a -af rubberband=tempo=1.04166 -c:a pcm_s16le out.mkv