You don't have to press ESC every time — just keep typing, and it will disappear on its own ;-)

But if you want to turn it off completely, look for editor.parameterHints.enabled in the VSCode settings and disable it.
However, that will disable it for all languages.

If you only want to do this for Robot Framework files, open your user or workspace settings as JSON and add the following:

"[robotframework]": {
    "editor.parameterHints.enabled": true
}