audio/jack-example-tools: Update to 4 release.

ChangeLog: https://github.com/jackaudio/jack-example-tools/releases/tag/4

 * Fix a typo in alsa_in manpage
 * Fix source-code comments and manpage for jack_simple_client
 * Remove includes of non-standard alloca.h header

PR:		269414
Reported by:	dev@submerge.ch (maintainer)