Fix spelling typo in the threaded engines `tbbt` example
Fix spelling typo in the threaded engines `tbbt` example

LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3,LogtalkDotOrg/logtalk3