The keyword is: "standard". It's not possible to modify (this includes hiding) the actual tooltip because it's a browser native implementation, at least, not possible for major browser engines like Blink, Webkit and Gecko, namely Chromium, Safari and Firefox respectively.

References:

• HTML Specification for .reportValidity() behaviour: https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#report-validity-steps
• An once-possible answer: https://stackoverflow.com/a/5965505

<form novalidate> ... </form>