What Krayt Dragon? I did not see or hear any in that scene ...
... In fact, I didn't see or hear any Krayt Dragon in the entire movie.
... or in any Star Wars movie whatsoever.
From the time I first saw the movie in the early '80s up until the mid-00's, I had always thought that it was supposed to be a Tusken yell of suprise from seeing Obi-Wan. The sound sounded a lot like a Tusken, but in a higher pitch as if surprised and afraid. Either they were generally afraid of strangers walking in on them when they are doing something bad, and/or they recognized Obi-Wan and knew him to be a bad-ass whom they did not want to mess with ... Even worse would be if a vigilante whom they knew could easily kick their asses, and who probably would do so if he witnessed them doing something bad would walk in on them when they were doing something bad.
This is the explanation that makes the most sense to me, and the one that I prefer. Therefore, I would prefer that a fan-edit or a future release of Star Wars either restore the original call or make it sound more like a Tusken.
As far as I am concerned, "Krayt Dragons" are not part of canon.