It seems that this is a new feature in JQuery UI 1.9.0, because I used JQuery UI plenty of times before and this text never poped up.
Couldn't find anything related on the API documentation.
So using an basic autocomplete example with local source
$( "#find-subj" ).autocomplete({
source: availableTags
});
When the search matches it shows this related helper text:
'1 result is available, use up and down arrow keys to navigate.'
How can I disable it in a nice way, not by removing it with JQuery selectors.