At what time stretching ratio would an audiophile notice a wrong pitch
Audiophiles don't hear anything unless they are told what to expect.

Joke aside, this is equivalent to transposition by a bit less than a semitone. The effect won't be noticed on voices - this is way too low for any kind "chipmunk" effect to be observed. As for music, some people very familiar with the original music might detect the change of tonality and/or tempo. But such stretching ratios are not unusual at all - DJs doing beat-matching, TV channels speeding up a sitcom to squeeze in more ads, and many, many movie to video conversions (telecine) have routinely used it.