LinkedIn.com imported contacts, filter out connections that do not have a LinkedIn account.
Navigate to https://www.linkedin.com/people/contacts, open your browser Developer console and run;
[].forEach.call(document.querySelectorAll('li.vcard'), function(el) {
if (!el.querySelector('span.in-icon')) {
el.parentNode.removeChild(el);
}
});
Your contacts that do not have LinkedIn accounts will be removed.